CN104064243A - Sandwiched parallel connection type PIN type alpha irradiation battery and preparation method thereof - Google Patents

Abstract

The invention discloses a sandwiched parallel connection type PIN type alpha irradiation battery and a preparation method thereof. At present, a nuclear battery has problems of low energy transformation ratio and low output power, and the invention is mainly used to solve the problems. The sandwiched parallel connection type PIN type alpha irradiation battery of the invention comprises an upper PIN junction and a lower PIN junction which are connected in parallel and an alpha radiation source layer. The lower PIN junction comprises an N-type ohmic contact electrode, an N-type highly-doped 4H-SiC substrate, an N-type lightly-doped epitaxial layer, a P-type highly-doped epitaxial layer and a P-type ohmic contact electrode from down to up successively. The structure distribution of the upper PIN junction from top to bottom is the same as the structure distribution of the lower PIN junction from down to up. The alpha radiation source layer is sandwiched between the P-type ohmic contact electrodes of the upper PIN junction and the lower PIN junction so as to realize the full utilization of high-energy alpha particles. According to the invention, advantages of large radiation source and semiconductor contact area, high nuclear raw material utilization rate and energy collection rate and large battery output voltage can be realized, and the battery can be used to supply power to a small circuit in a lasting manner or supply power in unattended occasions which need to be powered for a long time, such as polar regions, desert, etc.

Description

Sandwich parallel PIN type alpha irradiation battery and preparation method thereof

Technical field

The invention belongs to microelectronic, relate to semiconductor device structure and preparation method, specifically a kind of silicon carbide-based sandwich parallel PIN type alpha irradiation battery and preparation method thereof, can be used for the small circuit such as minute mechanical and electrical system and Aero-Space, deep-sea, polar region etc. needs long-term power supply and unattended occasion.

Technical background

Along with people are for the demand of low-power consumption, long-life, high reliability and small size power-supply unit, and concern to nuclear waste disposal, minisize nuclear battery becomes and receives much concern.Minisize nuclear battery is because its outstanding feature can be used to solve the long-term powerup issue of robot, implantable MEMS, wireless sensor node network, artificial cardiac pacemaker and Portable movable electronic product etc.And be expected to replace solar cell and thermoelectric (al) type radioisotope battery, solve at space flight and aviation field micro-/receive the long-term powerup issue of satellite, deep space unmanned probing device and ion propeller etc.

Nineteen fifty-three found by Rappaport research, and beta (β-Particle) radial energy that utilizes isotope to decay to produce produces electron-hole pair in semiconductor, and this phenomenon is called as β-VoltaicEffect.Nineteen fifty-seven, first Elgin-Kidde is used in β-VoltaicEffect power supply supply side, successfully produces first radioisotope micro battery β-VoltaicBattery.From 2006, along with the progress of semiconductor material with wide forbidden band SiC preparation and technology, there is the relevant report of the radioisotope micro battery based on SiC.

The Schottky junction type nuclear cell based on SiC that the people such as Guo Hui propose is disclosed by Zhang Lin in Chinese patent CN101325093A.Because schottky contact layer in this schottky junction nuclear battery covers whole cell area, incident particle arrives after device surface, capital is subject to stopping of schottky contact layer, only has part particle can enter device inside, and the particle that enters depletion region just can have contribution to the output power of battery.Therefore, the nuclear battery projectile energy loss of this structure is large, and energy conversion efficiency is lower.

Document " Demonstrationofa4HSiCbetavoltaiccell " has been introduced the C.I.Tomas by USA New York Cornell university, M.V.S.Chandrashekhar, and the people such as HuiLi have proposed silit PN junction formula nuclear battery.The substrate that this structure adopts is the highly doped substrate of P type, and immature in the existing technique of its Grown epitaxial loayer, therefore, easily introduces surface imperfection, and device creepage is large, and energy conversion rate is lower.

Document " Demonstrationofatadiationresistant; hightefficiencySiCbetavoltaic " has been introduced the C.J.Eiting by New Mexico QynergyCorporation, V.Krishnamoorthy and S.Rodgers, the people such as T.George have proposed silit p-i-n eliminant nuclear battery jointly, as shown in Figure 1.This PIN nuclear battery is followed successively by from top to bottom, radioactive source 7, P type Ohm contact electrode 6, the highly doped SiC layer 4 of P type, P type SiC layer 3, intrinsic i layer 2, the highly doped SiC substrate 1 of N-shaped and N-type Ohm contact electrode 5.In this structure, only have the raw charge carrier of irradiation in depletion layer and in a near minority diffusion length to be collected.And, for avoiding Ohm contact electrode to stop incident ion, P type Ohmic electrode is made in to a corner of device, make from P type Ohmic electrode the raw charge carrier of the irradiation away from transport process by compound, reduce energy transformation ratio, reduced the output current of battery.

Summary of the invention

The object of the invention is to the deficiency for above-mentioned prior art, propose a kind of sandwich parallel PIN type alpha irradiation battery and preparation method thereof, improve the utilization factor of αsource, thereby improve output current and the output voltage of battery.

Technical scheme of the present invention is achieved in that

One. sandwich parallel PIN type alpha irradiation battery of the present invention, comprising: PIN unit and αsource layer, is characterized in that:

Described PIN unit, adopts by the parallel connection of upper and lower two PIN knot and forms; Lower PIN knot is followed successively by from bottom to top, N-type Ohm contact electrode 5, the highly doped 4H-SiC substrate 1 of N-type, the low-doped epitaxial loayer 2 of N-type, the highly doped epitaxial loayer 3 of P type and P type Ohm contact electrode 4; Upper PIN knot is followed successively by from bottom to top, P type Ohm contact electrode 4, the highly doped epitaxial loayer 3 of P type, the low-doped epitaxial loayer 2 of N-type, the highly doped 4H-SiC substrate 1 of N-type and N-type Ohm contact electrode 5;

Described αsource layer 6, is clipped between the P type Ohm contact electrode 4 of upper and lower two PIN knot, to realize making full use of high-energyα-particle.

As preferably, it is 241 americium element that described αsource layer 6 adopts atomic mass, i.e. Am ²⁴¹.

As preferably, it is 238 plutonium element that described αsource layer 6 adopts atomic mass, i.e. Pu ²³⁸.

As preferably, the thickness h of described αsource layer 6 meets h≤m, and the average incident degree of depth of the high-energyα-particle that wherein m discharges for αsource in αsource material, is Am for αsource ²⁴¹, its value is: m=7.5 μ m is Pu for αsource ²³⁸, its value is: m=10 μ m.

As preferably, the thickness L of the low-doped epitaxial loayer 2 of described N-type meets L>=g, and wherein, the average incident degree of depth of the high-energyα-particle that g discharges for αsource in 4H-SiC, is Am for αsource ²⁴¹, its value is: i=10 μ m is Pu for αsource ²³⁸, its value is: i=18.2 μ m.

As preferably, it is lx10 that described substrate 1 adopts doping content ¹⁸cm ^-3n-type 4H-SiC, the highly doped epitaxial loayer 3 of P type and the low-doped epitaxial loayer 2 of N-type are 4H-SiC extension, wherein the doping content of the highly doped epitaxial loayer 3 of P type is 1x10 ¹⁹～5x10 ¹⁹cm ^-3, thickness is 0.1～0.2 μ m, the doping content of the low-doped epitaxial loayer 2 of N-type is 1x10 ¹⁵～2x10 ¹⁵cm ^-3.

Two. preparation method of the present invention comprises the following steps:

(1) make lower PIN knot:

1.1) clean: SiC print is cleaned, to remove surface contaminant;

1.2) the low-doped epitaxial loayer of growth N-type: utilizing the SiC print surface epitaxial growth one deck doping content of chemical vapor deposition CVD method after cleaning is 1x10 ¹⁵～2x10 ¹⁵cm ^-3, thickness is the low-doped epitaxial loayer of the N-type of 15～30 μ m;

1.3) the highly doped epitaxial loayer of growing P-type: utilizing chemical vapor deposition CVD method is 1x10 in the low-doped epi-layer surface epitaxial growth of N-type one deck doping content ¹⁹～5x10 ¹⁹cm ^-3, thickness is the highly doped epitaxial loayer of P type of 0.1～0.2 μ m;

1.4) depositing metal Ohm contact electrode: utilize electron-beam vapor deposition method at the highly doped epi-layer surface of P type and the SiC substrate Ni metal level that back side deposition thickness of extension is not 300nm, respectively as P type Ohm contact electrode and N-type Ohm contact electrode; Short annealing 3 minutes in nitrogen atmosphere at 1100 DEG C.。

(2) repeating step 1.1) to step 1.4) PIN ties in makings.

(3) utilize molecular plating the P type Ohm contact electrode of lower PIN knot or on plate the αsource that a layer thickness is 3～6 μ m on the P type Ohm contact electrode of PIN knot.

(4) utilize bonding method that the P type Ohm contact electrode one side of upper PIN knot and the P type Ohm contact electrode one side of lower PIN knot are pressed together, complete the making of sandwich parallel PIN type alpha irradiation battery.

The present invention compared with prior art tool has the following advantages:

1. the present invention is because the energy gap 4H-SiC of the backing material adopting is larger than the energy gap of traditional Si, and radiation-resisting performance is better, can reduce the damage of high-energyα-particle to device, improves the operating voltage of battery, extends the serviceable life of battery simultaneously;

2, the present invention is because the low-doped epitaxy layer thickness of N-type of extension is not less than high-energyα-particle that αsource the discharges average incident degree of depth in 4H-SiC, can reduce the decay of high-energyα-particle in the low-doped epitaxial loayer of N-type, make high-energyα-particle concentrate on the highly doped epitaxial loayer of P type and near the space charge region of the low-doped epitaxial layer interface of N-type, improve energy transformation ratio;

3, the present invention is because the thickness of the highly doped epitaxial loayer of P type is 0.1～0.2 μ m, the thickness of αsource layer is not more than the twice of high-energyα-particle that αsource the discharges average incident degree of depth in αsource material, can reduce the decay of high-energyα-particle in the highly doped epitaxial loayer of P type and αsource layer, improve collection of energy rate;

4, the present invention is owing to αsource layer being clipped between the P type Ohm contact electrode of upper and lower two PIN knot, compare to the upper surface that prior art is placed on radioactive source on battery, save αsource material, improved the utilization factor of αsource, thereby improved the capacity usage ratio of battery;

5, the present invention, due to by two in parallel placements of PIN knot, has improved the output voltage of battery.

Brief description of the drawings

Fig. 1 is the schematic cross-section of existing PIN nuclear battery;

Fig. 2 is the schematic cross-section of the sandwich parallel PIN type alpha irradiation battery of the present invention;

Fig. 3 is the schematic flow sheet that the present invention makes sandwich parallel PIN type alpha irradiation battery.

Embodiment

With reference to Fig. 2, irradiation battery of the present invention, comprising: PIN unit and αsource layer, and PIN unit is made up of the parallel connection of upper and lower two PIN knot; Lower PIN knot is followed successively by from bottom to top, N-type Ohm contact electrode 5, the highly doped 4H-SiC substrate 1 of N-type, the low-doped epitaxial loayer 2 of N-type, the highly doped epitaxial loayer 3 of P type and P type Ohm contact electrode 4; Upper PIN knot is followed successively by from bottom to top, P type Ohm contact electrode 4, the highly doped epitaxial loayer 3 of P type, the low-doped epitaxial loayer 2 of N-type, the highly doped 4H-SiC substrate 1 of N-type and N-type Ohm contact electrode 5; αsource layer 6 is clipped between the P type Ohm contact electrode 4 of upper and lower two PIN knot, and its thickness h meets h≤m, and the average incident degree of depth of the high-energyα-particle that wherein m discharges for αsource in αsource material, is Am for αsource ²⁴¹, its value is: m=7.5 μ m is Pu for αsource ²³⁸, its value is: m=10 μ m.

Battery in working order under, the high-energyα-particle radiating from αsource layer 6 is injected into the space charge region of the highly doped epitaxial loayer 3 of P type and low-doped epitaxial loayer 2 near interfaces of N-type through the P type Ohm contact electrode 4 of upper and lower two PIN knot, and then excite charge carrier, form output current.

With reference to Fig. 3, the method that the present invention makes sandwich parallel PIN type alpha irradiation battery provides following three embodiment:

Embodiment 1, preparing αsource is Am ²⁴¹, radioactive source layer thickness is the sandwich parallel PIN type alpha irradiation battery of 6 μ m.

Step 1: make lower PIN knot.

(1.1) clean 4H-SiC print, to remove surface contaminant, as shown in Fig. 3 (a).

(1.1.1) be lx10 by doping content ¹⁸cm ^-3highly doped N-shaped 4H-SiC substrate print at NH ₄oH+H ₂o ₂reagent soaks sample 10min, takes out post-drying, to remove sample surfaces organic remains;

(1.1.2) the 4H-SiC print of removing after surperficial organic remains is re-used to HCl+H ₂o ₂reagent soaks sample 10min, takes out post-drying, to remove ionic contamination.

(1.2) the low-doped epitaxial loayer of epitaxial growth N-type, as shown in Fig. 3 (b).

On SiC print after cleaning, utilize the N-type doped epitaxial layer of chemical vapor deposition CVD method epitaxial growth nitrogen doping.Its process conditions are: epitaxial temperature is 1570 DEG C, and pressure is 100mbar, and reacting gas is silane and propane, and carrier gas is pure hydrogen, and magazine source is liquid nitrogen, and obtaining nitrogen doped concentration is 1x10 ¹⁵cm ^-3, thickness is the low-doped epitaxial loayer of the N-type of 15 μ m.

(1.3) the highly doped epitaxial loayer of epitaxial growth P type, as shown in Fig. 3 (c).

On the low-doped epitaxial loayer of N-type of growth, utilize the highly doped epitaxial loayer of P type of chemical vapor deposition CVD method epitaxial growth aluminium doping, its process conditions are: epitaxial temperature is 1570 DEG C, pressure is 100mbar, reacting gas is silane and propane, carrier gas is pure hydrogen, impurity source is trimethyl aluminium, and obtaining aluminium doping content is 1x10 ¹⁹cm ^-3, thickness is the highly doped epitaxial loayer of P type of 0.1 μ m.

(1.4) deposit Ohm contact electrode, as shown in Fig. 3 (d).

(1.4.1) the SiC print completing after the highly doped outer layer growth of P type is carried out to RCA standard cleaning;

(1.4.2) print after cleaning is put on the microslide of electron beam evaporation deposition machine, adjusting microslide is 50cm to the distance of target, and reaction chamber pressure is evacuated to 5 × 10 ^-4pa, adjusting line is 40mA, the Ni metal level that is 300nm in surface deposition a layer thickness of the highly doped epitaxial loayer of the P of SiC print type, as P type Ohm contact electrode;

(1.4.3) utilize electron-beam vapor deposition method, at the substrate Si C Ni metal level that back side deposition thickness of extension is not 300nm, as N-type Ohm contact electrode.

(1.4.4) at 1100 DEG C, short annealing 3 minutes in nitrogen atmosphere.

Step 2: PIN knot in making.

Repeating step (1.1), to step (1.4), obtains PIN knot.

Step 3: utilize molecular plating to plate the αsource that a layer thickness is 6 μ m on the P type Ohm contact electrode of lower PIN knot, as shown in Fig. 3 (e).

Step 4: utilize bonding method, the αsource lamination on the P type Ohm contact electrode of the P type Ohm contact electrode of upper PIN knot and lower PIN knot is combined, obtain sandwich parallel PIN type alpha irradiation battery, as shown in Fig. 3 (f).

Embodiment 2, preparing αsource is Am ²⁴¹, radioactive source layer thickness is the sandwich parallel PIN type alpha irradiation battery of 5 μ m.

Step 1: make lower PIN knot.

1a) clean 4H-SiC print, to remove surface contaminant, as Fig. 3 (a).

This step is identical with the step (1.1) of embodiment 1.

The low-doped epitaxial loayer of 1b) epitaxial growth N-type, as Fig. 3 (b).

On SiC print after cleaning, utilize the N-type doped epitaxial layer of chemical vapor deposition CVD method epitaxial growth nitrogen doping.Its process conditions are: epitaxial temperature is 1570 DEG C, and pressure is 100mbar, and reacting gas is silane and propane, and carrier gas is pure hydrogen, and magazine source is liquid nitrogen, and completing nitrogen doped concentration is 1.5x10 ¹⁵cm ^-3, thickness is the growth of the low-doped epitaxial loayer of N-type of 25 μ m.

1c) the highly doped epitaxial loayer of epitaxial growth P type, as Fig. 3 (c).

On the low-doped epitaxial loayer of N-type of growth, utilize the highly doped epitaxial loayer of P type of chemical vapor deposition CVD method epitaxial growth Al-doping, its process conditions are: epitaxial temperature is 1570 DEG C, pressure is 100mbar, reacting gas is silane and propane, carrier gas is pure hydrogen, impurity source is trimethyl aluminium, and completing aluminium doping content is 3x10 ¹⁹cm ^-3, thickness is the growth of the highly doped epitaxial loayer of P type of 0.15 μ m.

1d) depositing metal contact electrode, as Fig. 3 (d).

This step is identical with the step (1.4) of embodiment mono-.

Step 2: PIN knot in making.

Repeating step 1a) to step 1d), obtain PIN knot.

Step 3: utilize molecular plating to plate the αsource that a layer thickness is 5 μ m on the P type Ohm contact electrode of upper PIN knot, as shown in Fig. 3 (e).

Step 4: utilize bonding method, the P type Ohm contact electrode of the αsource layer on the P type Ohm contact electrode of upper PIN knot and lower PIN knot is pressed together, obtain sandwich parallel PIN type alpha irradiation battery, as shown in Fig. 3 (f).

Embodiment 3, preparing αsource layer is Pu ²³⁸, radioactive source layer thickness is the sandwich parallel PIN type alpha irradiation battery of 3 μ m.

Steps A: PIN knot in making.

(A1) clean 4H-SiC print, to remove surface contaminant, as Fig. 3 (a).

This step is identical with the step (1.1) of embodiment 1.

(A2) the low-doped epitaxial loayer of N-type that utilizes chemical vapor deposition CVD method epitaxial growth nitrogen to adulterate on the SiC print after cleaning.Its process conditions are: epitaxial temperature is 1570 DEG C, and pressure is 100mbar, and reacting gas is silane and propane, and carrier gas is pure hydrogen, and magazine source is liquid nitrogen.Obtaining nitrogen doped concentration is 2x10 ¹⁵cm ^-3, thickness is that the low-doped epitaxial loayer of the N-type of 30 μ m is as Fig. 3 (b).

(A3) on the low-doped epitaxial loayer of N-type of growth, utilize the highly doped epitaxial loayer of P type of chemical vapor deposition CVD method epitaxial growth Al-doping, its process conditions are: epitaxial temperature is 1570 DEG C, pressure is 100mbar, reacting gas is silane and propane, carrier gas is pure hydrogen, impurity source is trimethyl aluminium, and obtaining aluminium doping content is 5x10 ¹⁹cm ^-3, thickness is that the highly doped epitaxial loayer of P type of 0.2 μ m is as Fig. 3 (c).

(A4) depositing metal contact electrode, as Fig. 3 (d).

This step is identical with the step (1.4) of embodiment mono-.

Step B: PIN knot in making.

Repeating step (A1), to step (A4), obtains PIN knot.

Step C: utilize molecular plating to plate a layer thickness respectively on the P type Ohm contact electrode of upper PIN knot and the P type Ohm contact electrode of lower PIN knot to be the αsource of 3 μ m, as Fig. 3 (e).

Step D: the αsource lamination on the P type Ohm contact electrode of the αsource layer on the P type Ohm contact electrode of upper PIN knot and lower PIN knot is combined, obtains sandwich parallel PIN type alpha irradiation battery, as Fig. 3 (f).

Claims (7)

1. a sandwich parallel PIN type alpha irradiation battery, comprising: PIN unit and αsource layer, is characterized in that:

Described PIN unit, adopts by the parallel connection of upper and lower two PIN knot and forms; Lower PIN knot is followed successively by from bottom to top, N-type Ohm contact electrode (5), the highly doped 4H-SiC substrate of N-type (1), the low-doped epitaxial loayer of N-type (2), the highly doped epitaxial loayer of P type (3) and P type Ohm contact electrode (4); Upper PIN knot is followed successively by from bottom to top, P type Ohm contact electrode (4), the highly doped epitaxial loayer of P type (3), the low-doped epitaxial loayer of N-type (2), the highly doped 4H-SiC substrate of N-type (1) and N-type Ohm contact electrode (5);

Described αsource layer (6), is clipped between the P type Ohm contact electrode (4) of upper and lower two PIN knot, to realize making full use of high-energyα-particle.

2. battery according to claim 1, is characterized in that αsource layer (6) adopts the americium element that atomic mass is 241, i.e. Am ²⁴¹.

3. battery according to claim 1, is characterized in that αsource layer (6) adopts the plutonium element that atomic mass is 238, i.e. Pu ²³⁸.

4. according to the battery described in claim 1 or 2 or 3, the thickness h that it is characterized in that αsource layer (6) meets h≤m, the average incident degree of depth of the high-energyα-particle that wherein m discharges for αsource in αsource material is Am for αsource ²⁴¹, its value is: m=7.5 μ m is Pu for αsource ²³⁸, its value is: m=10 μ m.

5. according to the battery described in claim 1 or 2 or 3, the thickness L that it is characterized in that the low-doped epitaxial loayer of N-type (2) meets L>=g, wherein, the average incident degree of depth of the high-energyα-particle that g discharges for αsource in 4H-SiC, is Am for αsource ²⁴¹, its value is: i=10 μ m is Pu for αsource ²³⁸, its value is: i=18.2 μ m.

6. battery according to claim 1, is characterized in that it is l x10 that substrate (1) adopts doping content ¹⁸cm ^-3n-type 4H-SiC, the highly doped epitaxial loayer of P type (3) and the low-doped epitaxial loayer of N-type (2) are 4H-SiC extension, wherein the doping content of the highly doped epitaxial loayer of P type (3) is 1x10 ¹⁹～5x10 ¹⁹cm ^-3, thickness is 0.1～0.2 μ m, the doping content of the low-doped epitaxial loayer of N-type (2) is 1x10 ¹⁵～2x10 ¹⁵cm ^-3.

7. a preparation method for sandwich parallel PIN type alpha irradiation battery, comprises the following steps:

(1) make lower PIN knot:

1.1) clean: SiC print is cleaned, to remove surface contaminant;

1.2) the low-doped epitaxial loayer of growth N-type: utilizing the SiC print surface epitaxial growth one deck doping content of chemical vapor deposition CVD method after cleaning is 1x10 ¹⁵～2x10 ¹⁵cm ^-3, thickness is the low-doped epitaxial loayer of the N-type of 15～30 μ m;

1.3) the highly doped epitaxial loayer of growing P-type: utilizing chemical vapor deposition CVD method is 1x10 in the low-doped epi-layer surface epitaxial growth of N-type one deck doping content ¹⁹～5x10 ¹⁹cm ^-3, thickness is the highly doped epitaxial loayer of P type of 0.1～0.2 μ m;

1.4) deposit Ohm contact electrode: utilize electron-beam vapor deposition method at the highly doped epi-layer surface of P type and the SiC substrate Ni metal level that back side deposition thickness of extension is not 300nm, respectively as P type Ohm contact electrode and N-type Ohm contact electrode; Short annealing 3 minutes in nitrogen atmosphere at 1100 DEG C.

(2) repeating step 1.1) to step 1.4) PIN ties in makings.

(3) utilize molecular plating the P type Ohm contact electrode of lower PIN knot or on plate the αsource that a layer thickness is 3～6 μ m on the P type Ohm contact electrode of PIN knot.

(4) utilize bonding method that the P type Ohm contact electrode one side of upper PIN knot and the P type Ohm contact electrode one side of lower PIN knot are pressed together, complete the making of sandwich parallel PIN type alpha irradiation battery.