CN105448376B - Using the silicon carbide Schottky junction isotope battery and its manufacture method of αsource - Google Patents

Abstract

The invention discloses a silicon carbide Schottky junction isotope battery using an α-radiation source and a manufacturing method thereof, the purpose of which is to improve output power and energy conversion efficiency, and increase packaging density. The technical scheme adopted by the battery of the invention is as follows : Including a substrate composed of a SiC substrate, an N-type SiC epitaxial layer is arranged on the upper part of the substrate, a plurality of steps are arranged on the N-type SiC epitaxial layer, grooves are arranged between adjacent steps, and the plurality of There are grooves in the middle of the top of the steps, and an N-type SiC ohmic contact doped region is arranged in the groove, and an N-type ohmic contact electrode is arranged on the upper end of the N-type SiC ohmic contact doped region, and the N-type ohmic contact electrode The shape is the same as that of the N-type SiC ohmic contact doped region, the top of the step on both sides of the N-type ohmic contact electrode is provided with an α radiation source; the bottom of the groove between the adjacent steps is provided with a Schott base contact electrodes.

Description

Silicon carbide Schottky junction isotope cell using alpha radiation source and manufacturing method thereof

technical field

The invention relates to the technical field of semiconductor devices and semiconductor technology, in particular to a silicon carbide Schottky junction isotope cell using an alpha radiation source and a manufacturing method thereof.

Background technique

Isotope batteries use semiconductor diodes as energy-transducing elements, and use the ionization effect of charged particles produced by the decay of radioactive isotopes in semiconductor materials to convert nuclear radiation energy into electrical energy. In order to obtain a sufficiently high and long-term stable output power to accelerate its practical application, it is necessary to simultaneously optimize the design of both the transducer element and the radiation source.

In terms of radioactive sources, most of the current low-energy β radioactive sources (such as 63Ni, with an average particle energy of 17.1KeV) are used as energy sources, and their electron flux density is low; Intensity to increase the output power is of limited significance. If a high-energy β radiation source (such as 147Pm, etc.) is used, the effective absorption of irradiated carriers will be difficult due to the deep particle range. From the point of view of ionization energy collection, alpha radiation sources are ideal as energy sources. Taking 241Am as an example, the particle energy is high (5.5MeV) but the range is moderate (about 28μm in Si material), and it mainly deposits energy in the material in the form of ionization. If it is used as an energy source, it can effectively increase the output power of the battery; however Alpha particles are likely to cause radiation damage to semiconductor devices and reduce the service life of transducer elements.

Wide bandgap semiconductor materials represented by SiC and GaN have the advantages of large bandgap width and strong radiation resistance. The isotope battery transducer element made of it has high built-in potential and small leakage current. Higher open circuit voltage and energy conversion efficiency than silicon-based cells. At the same time, the superior radiation resistance characteristics of wide bandgap materials and devices also make it possible to use alpha radiation sources as energy sources for isotope batteries. Compared with SiC PiN diodes, SiC Schottky diodes have the advantages of mature technology and no dead layer on the surface of batteries, and have unique advantages when used as isotope batteries.

However, there are still many problems in the research of SiC-based isotope cells using α radiation sources. In particular, most of the isotope cells reported so far adopt a vertical structure, that is, the two electrodes of the diode are respectively located on the substrate and the epitaxial surface, and the low A thick epitaxial layer is doped to fully absorb radiation-generated carriers. This structure process is relatively simple, but it is not suitable for α-radiation sources, because according to the radiation volt theory, the irradiated carriers in the depletion region and within a minority carrier diffusion length near it can be collected. For SiC Schottky diodes, even if a low-doped epitaxial layer is used, the width of the depletion region is only 1-2um, while the minority carrier diffusion length in SiC materials is only a few um. Due to the deep range of α particles and the concentrated release of energy near the range, it is difficult to fully absorb the radiation-generated carriers in the depth of the material. At the same time, a thick epitaxial layer will also lead to a large series resistance of the device, thereby affecting the conversion efficiency. Therefore, developing a new device structure and fully absorbing the radiation-generated carriers deep in the material is the key to improving the conversion efficiency of the battery and promoting the practical use of α-radiation source isotope batteries as soon as possible.

Contents of the invention

In order to solve the problems in the prior art, the present invention proposes a silicon carbide Schottky junction isotope battery that can improve the output power and energy conversion efficiency, can increase the packaging density, is beneficial to integration, and has strong practicability. and methods of manufacture thereof.

In order to achieve the above object, the technical solution adopted in the present invention is:

A silicon carbide Schottky junction isotope cell using an alpha radiation source, comprising a substrate composed of a SiC substrate, an N-type SiC epitaxial layer is arranged on the upper part of the substrate, and several N-type SiC epitaxial layers are arranged on the N-type SiC epitaxial layer. Steps, grooves are arranged between adjacent steps, and the top middle positions of the several steps are all implanted with N-type SiC ohmic contact doping regions, and the upper end of the N-type SiC ohmic contact doping regions is flush with the top of the steps, N The upper end of the SiC ohmic contact doped region is provided with an N-type ohmic contact electrode, the shape of the N-type ohmic contact electrode is the same as that of the N-type SiC ohmic contact doped region, and the steps on both sides of the N-type ohmic contact electrode An alpha radiation source is arranged on the top position; a schottky contact electrode is arranged at the bottom of the groove between the adjacent steps.

The step height on the N-type SiC epitaxial layer is 5 μm-15 μm, the step width is 10 μm-20 μm, and the distance between the steps is 2 μm-5 μm.

The overall thickness of the N-type SiC epitaxial layer is 10 μm˜30 μm.

The width of the Schottky contact electrode is the same as the step pitch.

The Schottky contact electrode includes a first layer of electrodes and a second layer of electrodes arranged in sequence from bottom to top, the first layer of electrodes is a Ni layer, Ti layer or Pt layer, and the thickness of the first layer of electrodes is 50nm~ 100nm, the second electrode layer is an Al layer with a thickness of 1000nm-2000nm.

The widths of the N-type SiC ohmic contact doped region and the N-type ohmic contact electrode are both 0.5 μm˜2 μm.

The N-type ohmic contact electrode includes a Ni layer and a Pt layer arranged in sequence from bottom to top, the thickness of the Ni layer is 200nm-400nm, and the thickness of the Pt layer is 50nm-200nm.

A method for manufacturing a silicon carbide Schottky junction isotope cell using an alpha radiation source, comprising the following steps:

Step 1, providing a substrate composed of a SiC substrate;

Step 2, epitaxially growing an N-type SiC epitaxial layer with a doping concentration of 1×10 ¹⁶ cm ^-3 to 5×10 ¹⁷ cm ^-3 and a thickness of 10 μm to 30 μm on the upper surface of the substrate by chemical vapor deposition;

Step 3. Using SF ₆ gas, etch several steps with a height of 5 μm to 15 μm, a width of 10 μm to 20 μm, and a spacing of 2 μm to 5 μm on the N-type SiC epitaxial layer by reactive ion dry etching, adjacent to each other. Grooves are provided between the steps;

Step 4, forming an N-type SiC ohmic contact doped region with a doping concentration of 1×10 ¹⁸ cm ^-3 to 1×10 ¹⁹ cm ^-3 on the N-type SiC epitaxial layer by ion implantation;

Step 5, depositing a Ni layer and a Pt layer sequentially above the N-type SiC ohmic contact doped region, the thickness of the Ni layer is 200nm-400nm, and the thickness of the Pt layer is 50nm-200nm;

Step 6. Perform thermal annealing at a temperature of 950° C. to 1050° C. under N atmosphere, and form an N _- type ohmic contact electrode composed of a first Ni layer and a Pt layer on the upper part of the N-type SiC ohmic contact doped region;

Step 7. Sputtering the first layer electrode and the second layer electrode sequentially at the bottom of the trench between the steps of the N-type SiC epitaxial layer to form a Schottky contact electrode composed of the first layer electrode and the second layer electrode. One layer of electrode is a Ni layer, Ti layer or Pt layer with a thickness of 50nm to 100nm, and the second layer of electrode is an Al layer with a thickness of 1000nm to 2000nm;

Step 8. Remove the N-type ohmic contact electrodes at both ends of the top of the step, keep only the N-type ohmic contact electrode in the middle, and set an α radiation source in the area where the N-type ohmic contact electrode is removed on the top of the step, that is, obtain carbonization using an α radiation source. Silicon Schottky junction isotope cell.

Compared with the prior art, the silicon carbide PIN type isotope cell of the α radiation source of the present invention is provided with several steps on the N-type SiC epitaxial layer, grooves are arranged between adjacent steps, and Schott is arranged at the bottom of the grooves. The base contact electrode uses a groove structure to make the Schottky contact deep into the I layer, which can effectively enhance the absorption of irradiated carriers near the alpha particle range, and improve the output power and energy conversion efficiency. Because the traditional structure mainly relies on the Schottky depletion region to collect the irradiated carriers, the Schottky contact electrode will cause the loss of incident particle energy; The neutral region collects the irradiated carriers and no longer depends on the area of the Schottky electrode, thus effectively reducing the energy loss of the incident particles and improving the energy conversion efficiency.

For devices with a vertical structure, the doping concentration of the I region will affect multiple parameters such as the open circuit voltage, the thickness of the sensitive region, and the series resistance, and it is difficult to compromise; while the lateral structure uses a neutral region to collect radiation-generated carriers. The distance between the special base contact electrode and the N-type ohmic contact electrode is determined by the minority carrier diffusion length, so the open-circuit voltage can be increased by appropriately increasing the doping concentration of the N-type SiC epitaxial layer in the I region, and the series resistance can be reduced. The design is more flexible. At the same time, it can effectively improve the radiation tolerance, which is more significant for isotope batteries using alpha radiation sources. The battery of the present invention adopts a horizontal device structure, and since there is no influence of the substrate, it is easy to obtain a series resistance lower than that of the vertical structure, thereby improving the filling factor. The invention adopts a lateral structure, can thin the substrate to reduce the volume of the battery, improves the package density, and facilitates the integration of the micro-nuclear battery into the MEMS microsystem. The device structure of the invention is not as sensitive to the thickness of the Schottky contact electrode metal layer as the vertical structure, and is easy to realize in technology.

The manufacturing method of the present invention adopts reactive ion dry etching method to etch several steps on the N-type SiC epitaxial layer, arranges grooves between adjacent steps, and adopts ion implantation method to form on the top of the steps of the N-type SiC epitaxial layer. N-type SiC ohmic contact doped region, deposit Ni layer and Pt layer sequentially above the N-type SiC ohmic contact doped region to form N-type ohmic contact electrode, and sputter in sequence at the bottom of the groove between the steps of the N-type SiC epitaxial layer The second Ni layer and Al layer form the Schottky contact electrode, and the Schottky contact goes deep into the I layer, which can effectively enhance the absorption of radiation-generated carriers near the alpha particle range, and improve the output power and energy conversion. Efficiency, the horizontal device structure is adopted. Since there is no influence of the substrate, it is easy to obtain a lower series resistance than the vertical structure, thereby improving the fill factor. At the same time, the substrate can be thinned to reduce the volume of the battery and increase the packaging density. The manufacturing method of the invention has the advantages of simple process, convenient realization and low cost, and the obtained battery has strong practicability and high popularization and application value.

Description of drawings

Fig. 1 is the structural representation of battery of the present invention;

Fig. 2 is the flowchart of manufacturing method of the present invention;

Figure 3a is a schematic diagram of the battery structure after the completion of step 2 of the manufacturing method of the present invention, Figure 3b is a schematic diagram of the battery structure after the completion of step 3, Figure 3c is a schematic diagram of the battery structure after the completion of step 4, and Figure 3d is a schematic diagram of the battery structure after the completion of steps 5 and 6 Schematic diagram of the battery structure, Figure 3e is a schematic diagram of the battery structure after step 7 is completed;

Among them, 1-substrate; 2-N-type SiC epitaxial layer; 3-N-type SiC ohmic contact doped region; 4-Schottky contact electrode; 5-N-type ohmic contact electrode; 6-α radiation source.

detailed description

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

Referring to Fig. 1, a silicon carbide Schottky junction isotope cell using an α-radiation source includes a substrate 1 composed of a SiC substrate, an N-type SiC epitaxial layer 2 is arranged on the upper part of the substrate 1, and the N-type SiC epitaxial layer There are several steps on 2, and grooves are arranged between adjacent steps. The height of the steps on the N-type SiC epitaxial layer 2 is 5 μm to 15 μm, the width of the steps is 10 μm to 20 μm, and the distance between the steps is 2 μm to 5 μm. The overall thickness of the N-type SiC epitaxial layer 2 is 10 μm to 30 μm, and an N-type SiC ohmic contact doped region 3 is implanted in the middle of the top of several steps, and the upper end of the N-type SiC ohmic contact doped region 3 is flush with the top of the steps, N An N-type ohmic contact electrode 5 is provided at the upper end of the N-type SiC ohmic contact doped region 3, the shape of the N-type ohmic contact electrode 5 is the same as that of the N-type SiC ohmic contact doped region 3, and the N-type SiC ohmic contact doped The widths of the region 3 and the N-type ohmic contact electrode 5 are both 0.5 μm to 2 μm, and the N-type ohmic contact electrode 5 includes a Ni layer and a Pt layer arranged in sequence from bottom to top, and the thickness of the Ni layer is 200 nm to 400 nm, and the Pt layer is The thickness of the layer is 50 nm to 200 nm. An α-radiation source 6 is arranged on the top of the step on both sides of the N-type ohmic contact electrode 5; a Schottky contact electrode 4 is arranged at the bottom of the groove between adjacent steps, and the width of the Schottky contact electrode 4 is the same as the step spacing The Schottky contact electrode 4 includes a first layer of electrodes and a second layer of electrodes arranged in sequence from bottom to top, the first layer of electrodes is a Ni layer, Ti layer or Pt layer, and the thickness of the first layer of electrodes is 50nm to 100nm, The second electrode is an Al layer with a thickness of 1000nm-2000nm.

Referring to Fig. 2, a method for manufacturing a silicon carbide Schottky junction isotope cell using an alpha radiation source comprises the following steps:

Step 1, providing a substrate 1 composed of a SiC substrate;

Step 2: Epitaxially grow an N-type SiC epitaxial layer 2 with a doping concentration of 1×10 ¹⁶ cm ^-3 to 5×10 ¹⁷ cm ^-3 and a thickness of 10 μm to 30 μm on the upper surface of the substrate 1 by chemical vapor deposition , the resulting battery structure is shown in Figure 3a;

Step 3: Using SF ₆ gas, etch a number of steps with a height of 5 μm to 15 μm, a width of 10 μm to 20 μm, and a spacing of 2 μm to 5 μm on the N-type SiC epitaxial layer 2 by reactive ion dry etching. Grooves are set between adjacent steps, and the resulting battery structure is shown in Figure 3b;

Step 4: Form an N-type SiC ohmic contact doped region 3 with a doping concentration of 1×10 ¹⁸ cm ^-3 to 1×10 ¹⁹ cm ^-3 on the N-type SiC epitaxial layer 2 by ion implantation, and the obtained battery The structure is shown in Figure 3c;

Step 5, depositing a Ni layer and a Pt layer sequentially above the N-type SiC ohmic contact doped region 3, the thickness of the Ni layer is 200nm-400nm, and the thickness of the Pt layer is 50nm-200nm;

Step 6. Perform thermal annealing at a temperature of 950° C. to 1050° C. for two minutes under N ₂ atmosphere, and form an N-type ohmic contact electrode 5 composed of a Ni layer and a Pt layer on the upper part of the N-type SiC ohmic contact doped region 3 , The resulting battery structure is shown in Figure 3d;

Step 7: Sequentially sputter the first layer electrode and the second layer electrode at the bottom of the trench between the steps of the N-type SiC epitaxial layer 2 to form a Schottky contact electrode 4 composed of the first layer electrode and the second layer electrode , the first layer of electrodes is a Ni layer, Ti layer or Pt layer with a thickness of 50nm to 100nm, the second layer of electrodes is an Al layer with a thickness of 1000nm to 2000nm, and the obtained battery structure is shown in Figure 3e;

Step 8, remove the N-type ohmic contact electrodes 5 at both ends of the top of the step, keep only the N-type ohmic contact electrode 5 in the middle, and set the alpha radiation source 6 in the area where the N-type ohmic contact electrode 5 is removed on the top of the step, that is, as shown in the figure 1 shows a silicon carbide Schottky junction isotope cell using an alpha radiation source.

The present invention adopts the silicon carbide Schottky junction isotope battery of α radiation source to use groove structure to make the Schottky contact deep into the depth of layer I, which can effectively enhance the absorption of radiation-generated carriers near the range of α particles, and improve the output power and energy conversion efficiency. Because the traditional structure mainly relies on the Schottky depletion region to collect the irradiated carriers, the Schottky contact electrode will cause the loss of incident particle energy; The neutral region collects the irradiated carriers and no longer depends on the area of the Schottky electrode, thus effectively reducing the energy loss of the incident particles and improving the energy conversion efficiency.

For devices with a vertical structure, the doping concentration of the I region will affect multiple parameters such as the open circuit voltage, the thickness of the sensitive region, and the series resistance, and it is difficult to compromise; while the lateral structure uses a neutral region to collect radiation-generated carriers. The distance between the special base contact electrode and the N-type ohmic contact electrode is determined by the minority carrier diffusion length, so the open-circuit voltage can be increased by appropriately increasing the doping concentration of the N-type SiC epitaxial layer in the I region, and the series resistance can be reduced. The design is more flexible. At the same time, it can also effectively improve the radiation tolerance, which is more significant for isotope batteries using α-radiation sources. The battery of the present invention adopts a horizontal device structure. Since there is no influence of the substrate, it is easy to obtain a lower series connection than the vertical structure. Resistance, thereby improving the fill factor, and at the same time, the substrate can be thinned to reduce the volume of the battery, which improves the packaging density, which is conducive to the integration of the micro-nuclear battery into the MEMS microsystem, and the thickness of the metal layer of the Schottky contact electrode is not like the longitudinal structure. So sensitive, easy to realize on the craft. The manufacturing method of the present invention has simple process, convenient realization and low cost, and the obtained battery has strong practicability and high popularization and application value.

To sum up, the present invention is novel and reasonable in design, easy to realize, beneficial to improving the energy conversion efficiency and packaging density of isotope batteries using α-radiation sources, beneficial to integration, strong in practicability, and high in popularization and application value.

The above description is only a specific explanation of the present invention, and is not intended to limit the present invention. Any simple modifications, changes and equivalent structural changes made to the above embodiments according to the technical essence of the present invention still belong to the technical solution of the present invention. within the scope of protection.

Claims (6)

1. a silicon carbide Schottky junction isotope battery that adopts alpha radiation source, is characterized in that, comprises the substrate (1) that is made of SiC substrate, and substrate (1) top is provided with N-type SiC epitaxial layer ( 2), the N-type SiC epitaxial layer (2) is provided with several steps, and grooves are provided between adjacent steps, and the top and middle positions of the several steps are all implanted with N-type SiC ohmic contact doping region (3), the upper end of the N-type SiC ohmic contact doped region (3) is flush with the top of the step, and the upper end of the N-type SiC ohmic contact doped region (3) is provided with an N-type ohmic contact electrode (5), the N-type The shape of the ohmic contact electrode (5) is the same as that of the N-type SiC ohmic contact doped region (3), and an alpha radiation source (6) is arranged on the top of the steps on both sides of the N-type ohmic contact electrode (5) ; Schottky contact electrodes (4) are arranged at the bottom of the grooves between the adjacent steps, the height of the steps on the N-type SiC epitaxial layer (2) is 5 μm to 15 μm, the width of the steps is 10 μm to 20 μm, and the steps The distance between them is 2 μm to 5 μm, and the width of the Schottky contact electrode (4) is the same as the step distance. 2 . A silicon carbide Schottky junction isotope cell using an α radiation source according to claim 1 , wherein the overall thickness of the N-type SiC epitaxial layer ( 2 ) is 10 μm to 30 μm. 3 . 3. A kind of silicon carbide Schottky junction isotope cell adopting alpha radiation source according to claim 1, is characterized in that, described Schottky contact electrode (4) comprises the first that arranges successively from bottom to top A layer electrode and a second layer electrode, the first layer electrode is a Ni layer, Ti layer or Pt layer, the thickness of the first layer electrode is 50nm-100nm, and the second layer electrode is an Al layer, the thickness is 1000nm-2000nm . 4. A kind of silicon carbide Schottky junction isotope cell using alpha radiation source according to claim 1, characterized in that, the N-type SiC ohmic contact doping region (3) and the N-type ohmic contact The widths of the electrodes (5) are all 0.5 μm to 2 μm. 5. A kind of silicon carbide Schottky junction type isotope battery adopting alpha radiation source according to claim 4, is characterized in that, described N-type ohmic contact electrode (5) comprises the Ni layer that is arranged successively from bottom to top and a Pt layer, the thickness of the Ni layer is 200nm-400nm, and the thickness of the Pt layer is 50nm-200nm. 6. A method for manufacturing a silicon carbide Schottky junction isotope cell employing an alpha radiation source as claimed in any one of claims 1-5, characterized in that it comprises the following steps: Step 1, providing a substrate (1) composed of a SiC substrate; Step 2. Using chemical vapor deposition to epitaxially grow N-type SiC epitaxy with a doping concentration of 1×10 ¹⁶ cm ^-3 to 5×10 ¹⁷ cm ^-3 and a thickness of 10 μm to 30 μm on the upper surface of the substrate (1). layer(2); Step 3: Using SF ₆ gas, etch several steps with a height of 5 μm to 15 μm, a width of 10 μm to 20 μm, and a pitch of 2 μm to 5 μm on the N-type SiC epitaxial layer (2) by reactive ion dry etching , a groove is set between adjacent steps; Step 4: Forming an N-type SiC ohmic contact doped region (3) with a doping concentration of 1×10 ¹⁸ cm ^-3 to 1×10 ¹⁹ cm ^-3 on the N-type SiC epitaxial layer (2) by ion implantation ; Step 5, depositing a Ni layer and a Pt layer sequentially above the N-type SiC ohmic contact doped region (3), the thickness of the Ni layer is 200nm-400nm, and the thickness of the Pt layer is 50nm-200nm; Step 6. Perform thermal annealing at a temperature of 950°C to 1050°C under _N2 atmosphere, and form an N-type ohmic contact electrode (5) consisting of a Ni layer and a Pt layer on the upper part of the N-type SiC ohmic contact doped region (3). ); Step 7: Sequentially sputter the first layer electrode and the second layer electrode at the bottom of the groove between the steps of the N-type SiC epitaxial layer (2), forming a Schottky contact electrode composed of the first layer electrode and the second layer electrode (4), the first layer of electrodes is a Ni layer, Ti layer or Pt layer, with a thickness of 50nm to 100nm, and the second layer of electrodes is an Al layer, with a thickness of 1000nm to 2000nm; Step 8, remove the N-type ohmic contact electrodes (5) at both ends of the top of the step, keep only the middle N-type ohmic contact electrode (5), and set an alpha radiation source in the area where the N-type ohmic contact electrode (5) is removed on the top of the step (6), that is, a silicon carbide Schottky junction isotope cell using an alpha radiation source is obtained.