Silicon carbide single crystal x-ray detector and preparation method

Abstract

An X-ray detector based on silicon carbide single crystal as well as its preparation method. The detector mainly includes: high resistivity silicon carbide single crystal, high electron concentration n-type silicon carbide layer, low electron concentration n-type silicon carbide layer, high hole concentration p-type silicon carbide layer, low hole concentration p-type silicon carbide layer, silicon dioxide protection layer, p-type silicon carbide ohmic contact electrode, n-type silicon carbide ohmic contact electrode, and gold lead electrode. The invention provides an effective and simple process manufacturing technology, solves the preparation problem of silicon carbide-based high-energy X-ray detector, and realizes the development of a new silicon carbide radiation detector.

Claims

1. A silicon carbide single crystal X-ray detector, composed of a high resistivity silicon carbide single crystal, a high electron concentration n-type silicon carbide layer, a low electron concentration n-type silicon carbide layer, a high hole concentration p-type silicon carbide layer, a low hole concentration p-type silicon carbide layer, a silicon dioxide protection layer, a p-type silicon carbide ohmic contact electrode, an n-type silicon carbide ohmic contact electrode and a gold lead electrode; wherein the high resistance silicon carbide single crystal is the main structure; the n-type silicon carbide layer with high electron concentration is embedded on an upper surface of the high resistivity silicon carbide single crystal, and an upper surface of the two layers is even; the low electron concentration n-type silicon carbide layer is arranged around the high electron concentration n-type silicon carbide layer; the silicon dioxide protective layer is arranged around the n-type silicon carbide ohmic contact electrode, and it is integrally covered on the upper surface of the high resistance silicon carbide single crystal; the two gold lead electrodes are located on an upper surface of the junction of the silicon dioxide protective layer and the n-type silicon carbide ohmic contact electrode; the high hole concentration p-type silicon carbide layer is embedded on a lower surface of the high resistivity silicon carbide single crystal, and the upper surface of the two layers is even; the low hole concentration p-type silicon carbide layer is arranged around the high hole concentration p-type silicon carbide layer; the p-type silicon carbide ohmic contact electrode is an inverted T-type, and the top contacts with the high hole concentration p-type silicon carbide layer; a gap between the low hole concentration p-type silicon carbide layer and the p-type silicon carbide ohmic contact electrode is filled with the silicon dioxide protective layer, covering the lower surface of the high resistance silicon carbide single crystal.

2. A preparation method for a silicon carbide single crystal X-ray detector, comprising the following steps: step 1: graphical AlN ion implantation barrier layers were prepared on upper and lower surfaces of a high resistive silicon carbide single crystal by photolithographic mask assistant deposition; the barrier layers were AlN ion implantation barrier layer a10, AlN ion implantation barrier layer b11 and AlN ion implantation barrier layer c12; a thickness of the barrier layer a10 was 10 nm to 10 m, and a diameter of the barrier layer a10 was 50%90% of an edge length of a whole sample; a thickness of layer b11 is 10 nm15 m, and an annular width accounts for 5%30% of the edge length of the whole sample; a thickness of layer c12 is 10 nm20 m, covering all areas except for the a10 and b11; step 2: an n-type silicon carbide layer with transverse distribution of electron concentration and a p-type silicon carbide layer with transverse distribution of hole concentration were formed on an upper and lower surface of high-resistivity silicon carbide crystal by ion implantation and thermal annealing; a thickness of the n-type silicon carbide layer and the p-type silicon carbide layer was 10 nm to 10 m; the n-type silicon carbide layer consisted of a high-electron concentration n-type silicon carbide layer and a low-electron concentration n-type silicon carbide layer, the low electron concentration n-type silicon carbide layer are arranged around the electron concentration n-type silicon carbide layer, an electron concentration of the high electron concentration n-type silicon carbide layer is 5.010.sup.16 cm.sup.35.010.sup.19 cm.sup.3, and an electron concentration of the low electron concentration n-type silicon carbide layer is 5.010.sup.15 cm.sup.35.010.sup.18 cm.sup.3; the p-type silicon carbide layer includes a high hole concentration p-type silicon carbide layer and a low hole concentration p-type silicon carbide layer, the low hole concentration p-type silicon carbide layer is arranged around the high hole concentration p-type silicon carbide layer, a hole concentration of the high hole concentration p-type silicon carbide layer is 5.010.sup.16 cm.sup.35.010.sup.19 cm.sup.3, and a hole concentration of the low hole concentration p-type silicon carbide layer is 5.010.sup.15 cm.sup.35.010.sup.18 cm.sup.3; step 3: protect the AlN layer on the upper surface of SiC crystal, wet etch the AlN layer on the lower surface of SiC crystal, deposit a silicon dioxide layer on the lower surface of SiC crystal, use photolithography mask technology and HF wet etching technology to open holes on a silicon dioxide protection layer, use photolithography mask technology, deposition technology and thermal annealing technology to prepare a p-type silicon carbide ohmic junction contact electrode; among them, the thickness of the silicon dioxide protective layer is 10 nm10 m, the area of the open hole is the same as that of the high hole concentration p-type SiC layer 4, and a thickness of p-type SiC ohmic contact electrode is 10 nm15 m, and a width is between an edge of the open hole and an edge of the lower surface of SiC single crystal; step 4: wet etching of the AlN layer on the surface of silicon carbide single crystal, depositing silicon dioxide protective layer on the surface of the silicon carbide single crystal; using photolithographic mask technology and HF wet etching technology to open holes on the silicon dioxide protective layer; using photolithographic mask technology and coating technology to prepare a patterned n-type silicon carbide ohmic contact electrode; using photolithographic mask technology, deposition technology and thermal annealing technology to fabricate of a graphical gold lead electrode; among them, a thickness of silicon dioxide protective layer is 10 nm10 m; the area of open hole is the same as that of high electron concentration n-type silicon carbide layer; a thickness of n-type silicon carbide ohmic contact electrode is 10 nm15 m, and the area of open hole is the same; a thickness of gold lead electrode is 10 nm10 m, and a coverage area is between 10% of a surface edge of the high resistivity silicon carbide single crystal.

3. The preparation method of claim 2, wherein the corrosive solution is one or two mixtures of sodium hydroxide and potassium hydroxide.

4. The preparation method of claim 2, wherein the deposition methods are sol-gel method, thermal evaporation method, electron beam evaporation method, magnetron sputtering method, laser pulse deposition, atomic layer epitaxy or molecular beam epitaxy.

Description

DESCRIPTION OF DRAWINGS

(1) FIG. 1 is a schematic diagram of an X-ray detector based on silicon carbide single crystal.

(2) FIG. 2 is a top view of the device structure with an n-type silicon carbide contact electrode.

(3) FIG. 3 is a cross-sectional diagram of silicon carbide single crystal with an AlN ion implantation barrier layer.

(4) FIG. 4 is a graphic illustration of silicon carbide single crystal with an AlN ion implantation barrier layer.

(5) FIG. 5 is a schematic diagram of silicon carbide single crystal with AlN barrier layer after ion implantation and thermal annealing.

(6) FIG. 6 is a cross-sectional diagram of a device with a p-type silicon carbide contact electrode.

(7) FIG. 7 is a schematic diagram of the device structure with a p-type silicon carbide contact electrode.

(8) Figure: 1 high resistance silicon carbide single crystal; 2 high electron concentration n-type silicon carbide layer; 3 low electron concentration n-type silicon carbide layer; 4 high hole concentration p-type silicon carbide layer; 5 low hole concentration p-type silicon carbide layer; 6 silicon dioxide protective layer; 7 p-type silicon carbide ohmic contact electrode; 8 n-type silicon carbide ohmic contact electrode; 9 gold lead electrode; 10 AlN ion implantation barrier layer a; 11 AlN ion implantation barrier layer b; 12 AlN ion implantation barrier layer c.

DETAILED DESCRIPTION

(9) A detailed operation method of the invention is further illustrated with the following figures and technical plans.

EXAMPLE 1

(10) This example provides a method for proposing an X-ray detector based on silicon carbide single crystal, including the following process steps:

(11) Step 1: Select high resistivity silicon carbide single crystals with thickness of 200 um and surface of 5 mm square.

(12) Step 2: Graphical AlN ion implantation barrier layer was prepared on the upper and lower surfaces of high resistive silicon carbide single crystal 1 by multiple photolithographic mask assisted deposition. The thickness of AlN ion implantation barrier layer a10 is 50 nm and its diameter is 3 mm; the thickness of AlN ion implantation barrier layer b11 is 100 nm and its ring width is 0.5 mm; and the thickness of AlN ion implantation barrier layer c12 is 500 nm.

(13) Step 3: An n-type silicon carbide layer with transverse distribution of electron concentration and a p-type silicon carbide layer with transverse distribution of hole concentration were formed on the upper and lower surface of high-resistivity silicon carbide crystal 1 by ion implantation and thermal annealing; the thickness of high electron concentration n-type silicon carbide layer 2 and high hole concentration p-type silicon carbide layer 4 are 400 nm. The electron concentration of the high electron concentration n-type silicon carbide layer 2 is 1.010.sup.18 cm.sup.3. The hole concentration of the high hole concentration p-type silicon carbide layer 4 is 5.010.sup.17 cm.sup.3; the thickness of low electron concentration n-type silicon carbide layer 3 and low hole concentration p-type silicon carbide layer 5 are 350 nm. The electron concentration of the low electron concentration n-type silicon carbide layer 3 is 5.010.sup.17 cm.sup.3. The hole concentration of the low hole concentration p-type silicon carbide layer 5 is 1.010.sup.17 cm.sup.3;

(14) Step 4: Use wax to protect the AlN layer on the upper surface, use potassium hydroxide solution to corrode the AlN layer on the lower surface, deposit silicon dioxide protective layer 6; then use photolithography mask technology and HF wet etching technology to open holes on silicon dioxide protective layer 6; and then use photolithography mask technology, deposition technology and thermal annealing technology to prepare p-type ohmic contact electrode; The thickness of silicon dioxide protective layer 6 is 100 nm, the aperture diameter is 3 mm, the thickness of p-type silicon carbide ohmic contact electrode 7 is 200 nm and its diameter is 4 mm.

(15) Step 5: AlN layer on the upper surface was eroded by potassium hydroxide solution, and deposited silicon dioxide protective layer 6; then the photolithographic mask technology and HF wet etching technology were used to open holes on silicon dioxide protective layer 6; the n-type silicon carbide ohmic contact electrode 8 was fabricated by photolithographic mask technology and deposition technology; the thickness of silicon dioxide protective layer 6 was 100 nm; the diameter of the hole was 3 mm; The thickness of n-type silicon carbide ohmic contact electrode 8 is 100 nm and its diameter is 3 mm. Then the annular gold lead electrode 9 is prepared by photolithography mask technology, coating technology and thermal annealing technology. The outer ring diameter is 4 mm, the inner ring diameter is 2.6 mm, and the thickness is 500 nm.