CN103413860A - Preparation method of local region back surface passivated crystalline silicon cell - Google Patents

Abstract

The invention discloses a preparation method of a local region back surface passivated crystalline silicon cell. According to the preparation method, after the back surface of a silicon wafer is polished, a dense Al203 and SiNx double-layer lamination passivated film is prepared on the back surface of the silicon wafer, good passivation performance is obtained through annealing treatment, and a common field passivation method of an aluminum back surface field P+ layer is replaced. Before a front surface SiNx film is plated, acid cleaning liquid with an appropriate concentration is used for cleaning, and the passivation effect of the front surface is improved. An electrode lock region contact window is prepared on the back surface of the cell according to a designed graph open film. Finally, aluminum paste is printed and injected into the electrode window, and an aluminum-silicon alloy back electrode with a good contact effect is formed in a sintering mode. The cell prepared through the method can improve the back surface passivation effect and the light inner back reflection rate, namely the open-circuit voltage and short-circuit currents are improved, and therefore the efficiency of the cell is improved.

Description

A kind of preparation method of local passivating back crystal silicon cell

Technical field

The invention belongs to the preparation field of crystal silicon cell, a kind of preparation method who is easy to the local area back field passivation crystal silicon cell of industrialization production specifically is provided.

Background technology

Front photovoltaic industry enters the downturn period, and easy situation promotes the continuous merging and reorganization of photovoltaic enterprise, improves battery efficiency and has become the major way that each large photovoltaic enterprise breaks away from the industry crisis by promoting the battery technology of preparing.As the representative of high-efficiency crystal silicon cell, the local area back field passivating technique improves battery efficiency by the mode that employing reduces back of the body recombination-rate surface, compares with conventional aluminium back surface field battery, can make efficiency improve more than 1 percentage point; Particularly in the situation that the continuous attenuate of silicon wafer thickness, this kind technology is to improving battery efficiency and reducing the battery angularity and play very large effect.

Usually adopt the mode of ald or board-like PECVD deposition to prepare Al₂O₃Passivating film, preparation technology is relatively simple, and passivation effect is better than the standby SiO of PECVD legal system₂The SiO that the high-temperature thermal oxidation legal system is standby₂Inactivating performance is good, but this method is easily at the thicker SiO of front surface growth₂, and pyroprocess easily produces lattice defect in silicon, increase complex centre, is unfavorable for the raising of battery efficiency.Domesticly realized that several large photovoltaic enterprise of this kind battery volume production generally adopts Al₂O₃Do passivating film.

The mode that can be used for out film has multiple, comprising photoetching technique open embrane method, silk screen printing corrosivity slurry is opened embrane method, laser open embrane method etc.The laser machining accuracy is high, stability is strong, generally adopts at present the mode of laser open film to prepare the back side and opens film pattern.Each large slurry company strengthens the research and development of the aluminium paste be complementary, and existing many moneys aluminium paste of being suitable for the local area back field passivation comes out now, and true the demonstration, this kind local area back field passivation cell will become the main product in photovoltaic market very soon.

Summary of the invention

The purpose of this invention is to provide a kind of preparation method who is easy to a kind of local passivating back crystal silicon cell of industrialization production, on conventional production line, add the industrialization production that corollary equipment just can be realized this kind battery, do not cause conventional waste of producing line equipment, this kind preparation method is simple, newly-increased technological process can not cause additional injuries to battery, is convenient to industrialization production.The method can improve the interior back reflection rate of passivating back effect and light, and the battery of preparing has improved open circuit voltage and short circuit current, thereby improves battery efficiency.

For reaching above purpose, the technical solution used in the present invention is:

A kind of preparation method of local passivating back crystal silicon cell, concrete steps are:

(1) select the p type single crystal silicon sheet to make substrate, making herbs into wool on substrate, then prepare the P-N knot at front side of silicon wafer and the back side;

When (2) adopting alkaline corrosion liquid to remove back side P-N knot, realize polished backside;

(3) at the thick alundum (Al2O3) passivating film of silicon chip back side plating 5 nm～30nm, the silicon chip after plated film, through the high temperature anneal 20 min of 400 ℃～600 ℃～60min, is realized to passivating back;

(4) on the alundum (Al2O3) rete of silicon chip, plate silicon nitride film, described silicon nitride film thickness is 100 nm～180nm;

The silicon chip that (5) will be coated with after alundum (Al2O3) and silicon nitride dual layer passivation film cleans 5S～20S in mass fraction is 0.5%～1.5% HF solution, then at front side of silicon wafer plating silicon nitride anti-reflecting film, the thicknesses of layers of described silicon nitride anti-reflecting film is 60nm-90nm;

(6) adopt laser to open film pattern according to the wire set and open film;

(7) print successively in order back electrode, aluminium paste and silver slurry (adopting conventional screen printing mode), sintering in sintering furnace, form the alusil alloy layer; Described sintering temperature is 840 ℃～860 ℃.

Preferably, the P-N junction depth in step (1) is more than 0.4 μ m, and surface concentration is 0.9 * 10²⁰/ cm³～1.1 * 10²⁰/ cm³.

Preferably, in step (2), alkaline corrosion liquid used is NaOH solution or KOH solution, and the back side weighted average reflectivity after polishing is more than 70%.

Preferably, the described Al of step (3)₂O₃Thicknesses of layers is 10～15nm, and annealing temperature is 500～520 ℃, and annealing time is 25～30min.

Preferably, in step (4), silicon nitride (SiNx) thicknesses of layers is 120～150nm.

Preferably, in step (5), the HF mass fraction is 0.5%～1.0%, and scavenging period is 15～20S.

Preferably, in step (5), the thicknesses of layers of silicon nitride anti-reflecting film is 75nm.

Preferably, in step (6), laser used is pulsed or continous way P laser second, and wavelength is 310 nm～532nm, and power is 12 W～25W.

Preferably, the live width of opening the film threadlike graph described in step (6) is 40 μ m～45 μ m, and distance between centers of tracks is 1100 μ m～1300 μ m.Described die sinking is existing method.

Preferably, in step (7), the sintering temperature of sintering furnace is 850 ℃～860 ℃.

Below the present invention is further explained and illustrates:

Step (1) preferably adopts P type boron-doping monocrystalline silicon piece, and resistivity is 1～3 Ω cm, and the surperficial peak concentration of the emitter diffuseed to form is less than 1 * 10²⁰/ cm³.

Step (2) during polishing, adopts chain type alkalescence wet etching machine overleaf, when removing back side PN junction, removes the pyramid matte.

The mode that step (3) preferably adopts ald or microwave plasma to strengthen chemical vapour deposition (CVD) prepares Al at burnishing surface₂O₃, the silicon chip after plated film, through the high temperature anneal, is realized to passivating back;

Step (4) preferably adopts radio frequency PECVD equipment at silicon chip Al₂O₃Plating SiNx film on film;

Step (5) preferably adopts tubular type PECVD plating SiNx diaphragm.

It is that the laser of 310～532nm is opened film that step (6) preferably adopts wavelength, regulates laser focal, opens film speed and is preferably 300～1000mm/s.

It is 850 ℃～860 ℃ that step (7) preferably sets the sintering furnace temperature, and the sintering temperature of conventional batteries is 870～910 ℃.

Compared with prior art, advantage of the present invention is:

1, for ald or microwave type plasma reinforced chemical vapour deposition plating Al₂O₃Different modes, obtain corresponding best annealing process, silicon chip front and rear surfaces plating SiNx measures by WT-2000, effectively minority carrier life time is in the 40us left and right.

2, before the positive SiNx of plating, adopt the HF solution cleaning silicon chip of appropriate concentration, remove in each technological process the pollution to front surface, do not damage simultaneously the passivation effect of back side dual layer passivation film, with the battery of making without cleaning, compare, open circuit voltage improves 2mV, and wavelength is that the interior external quantum efficiency value of 1000nm infrared light is fully equal.

3, find appropriate laser open membrane process and sintering process, series resistance is in 2.5m Ω left and right, near the resistance of conventional batteries.

4, adopt the mode of laser or printing corrosivity slurry, according to the figure designed, open film at cell backside, prepare electrode local contact window, can reduce the electrode contact area, thereby reduce the electrode district leakage current.

5, the battery for preparing of the present invention can improve the interior back reflection rate of passivating back effect and light, namely improves open circuit voltage and short circuit current, thereby improves battery efficiency.

The accompanying drawing explanation

Fig. 1 is that film pattern is opened at the back side of embodiment 1 and 2, and wherein A means out the distance between centers of tracks of film pattern, and B means out the live width of film pattern, and C means the silicon chip substrate marginal texture.

Embodiment

The present invention is described further below in conjunction with embodiment.

Embodiment 1:

The present invention is according to the preparation method of local passivating back crystal silicon cell, and the P type of take is mixed the B monocrystalline silicon piece and is substrate, and concrete preparation flow is as follows:

(1) according to conventional monocrystalline alkali formula making herbs into wool mode making herbs into wool face, and the low surface concentration emitter of the dark knot of diffusion preparation, surperficial peak concentration is 1 * 10²⁰/ cm³～1.5 * 10²⁰/ cm³, sheet resistance is in 75 Ω/ left and right.

(2) adopt the polishing of chain type alkalescence wet etching machine, remove back side PN junction and matte.

(3) adopt microwave type plasma reinforced chemical vapour deposition equipment at burnishing surface, to prepare the Al of 20～25nm thickness₂O₃, to the silicon chip after plated film through 480 ℃ of high annealing 35min.

(4) adopt tubular type radio frequency PECVD equipment at silicon chip Al₂O₃Plating 120nm thickness SiNx diaphragm on film.

(5) in being 0.5% HF solution, cleaned 10～15 seconds mass fraction, and at the thick SiNx antireflective coating of diffusion P-N knot face plating 75nm.

(6) adopting P wavelength second is that the green (light) laser of 532nm is opened film, and setting power is 18～25W, and opening film speed is 300～500mm/s, and laser pulse frequency is 50～90KHZ.

(7) as shown in Figure 1, open the film live width is 40～50 μ m to the die sinking figure, and distance between centers of tracks is 1000～1100 μ m.

(8) printing back electrode, aluminium paste (purchasing and E.I.Du Pont Company) and positive silver (silver slurry), the sintering temperature of regulating sintering furnace is 850～860 ℃, after sintering, opens overleaf diaphragm area and realizes filling preferably and forming the alusil alloy layer.

With conventional batteries, compare, more than the open circuit voltage of battery prepared by this kind method can improve 6mV, more than short circuit current can improve 10mA.

Embodiment 2:

(1) according to conventional monocrystalline alkali formula making herbs into wool mode making herbs into wool face, and the low surface concentration emitter of the dark knot of diffusion preparation, surperficial peak concentration is 1 * 10²⁰/ cm³～1.2 * 10²⁰/ cm³, sheet resistance is in 85 Ω/ left and right.

(2) adopt the polishing of chain type alkalescence wet etching machine, remove back side PN junction and matte.

(3) adopt the ald mode at burnishing surface, to prepare the Al of 10～15nm thickness₂O₃, to the silicon chip after plated film through 500～520 ℃ of annealing temperature 25～30min.

(4) adopt tubular type radio frequency PECVD equipment at silicon chip Al₂O₃Plating 120nm thickness SiNx diaphragm on film.

(5) at mass fraction, be respectively the HF/H of 0.5% left and right₂O₂In solution, cleaned 15～20 seconds, and at the thick SiNx antireflective coating of diffusion P-N knot face plating 75nm.

(6) adopting P wavelength second is that the green (light) laser of 532nm is opened film, and setting power is 15～20W, and opening film speed is 300～500mm/s, and laser pulse frequency is 50～90KHZ.

(7) as shown in Figure 1, open the film live width is 40～45 μ m to the die sinking figure, and distance between centers of tracks is 1100～1300 μ m.

(8) printing back electrode, aluminium paste (purchasing and E.I.Du Pont Company) and positive silver (silver slurry), the sintering temperature of adjusting is 850～860 ℃, after sintering, opens overleaf diaphragm area and realizes filling preferably and forming the alusil alloy layer.

With conventional batteries, compare, more than the open circuit voltage of battery prepared by this kind method can improve 8mV, more than short circuit current can improve 15mA.

Claims (10)

1. the preparation method of a local passivating back crystal silicon cell, is characterized in that, concrete steps are:

(1) select the p type single crystal silicon sheet to make substrate, making herbs into wool on substrate, then prepare the P-N knot at front side of silicon wafer and the back side;

When (2) adopting alkaline corrosion liquid to remove back side P-N knot, realize polished backside;

(3) at the thick alundum (Al2O3) passivating film of silicon chip back side plating 5 nm～30nm, the silicon chip after plated film, through the high temperature anneal 20 min of 400 ℃～600 ℃～60min, is realized to passivating back;

(4) on the alundum (Al2O3) rete of silicon chip, plate silicon nitride film, described silicon nitride film thickness is 100 nm～180nm;

The silicon chip that (5) will be coated with after alundum (Al2O3) and silicon nitride dual layer passivation film cleans 5S～20S in mass fraction is 0.5%～1.5% HF solution, then at front side of silicon wafer plating silicon nitride anti-reflecting film, the thicknesses of layers of described silicon nitride anti-reflecting film is 60nm-90nm;

(6) adopt laser to open film pattern according to the wire set and open film;

(7) print successively in order back electrode, aluminium paste and silver slurry, sintering in sintering furnace, form the alusil alloy layer; The sintering temperature of described sintering furnace is 840 ℃～860 ℃.

2. the preparation method of local passivating back crystal silicon cell according to claim 1, is characterized in that, the P-N junction depth in step (1) is more than 0.4 μ m, and surface concentration is 0.9 * 10²⁰/ cm³～1.1 * 10²⁰/ cm³.

3. the preparation method of local passivating back crystal silicon cell according to claim 1, is characterized in that, the back side weighted average reflectivity in step (2) after polishing is more than 70%.

4. the preparation method of local passivating back crystal silicon cell according to claim 1, is characterized in that the described Al of step (3)₂O₃Thicknesses of layers is 10～15nm, and annealing temperature is 500～520 ℃, and annealing time is 25～30min.

5. the preparation method of local passivating back crystal silicon cell according to claim 1, is characterized in that, in step (4), the silicon nitride film layer thickness is 120 nm～150nm.

6. the preparation method of local passivating back crystal silicon cell according to claim 1, is characterized in that, in step (5), the HF mass fraction is 0.5%～1.0%, and scavenging period is 15～20S.

7. the preparation method of local passivating back crystal silicon cell according to claim 1, is characterized in that, in step (5), the thicknesses of layers of silicon nitride anti-reflecting film is 75nm.

8. the preparation method of local passivating back crystal silicon cell according to claim 1, is characterized in that, in step (6), laser used is pulsed or continous way P laser second, and wavelength is 310 nm～532nm, and power is 12 W～25W.

9. the preparation method of local passivating back crystal silicon cell according to claim 1, is characterized in that, the live width of opening the film threadlike graph described in step (6) is 40 μ m～45 μ m, and distance between centers of tracks is 110 μ m～1300 μ m.

10. the preparation method of local passivating back crystal silicon cell according to claim 1, is characterized in that, in step (7), the sintering temperature of sintering furnace is 850 ℃～860 ℃.

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