阅读说明：本技术 一种遂穿氧化钝化电池的制备方法 (Preparation method of tunneling oxidation passivation battery ) 是由 袁宁一 王芹芹 丁建宁 程广贵 王书博 于 2020-04-03 设计创作，主要内容包括：本发明属于太阳能光伏行业领域,尤其涉及一种遂穿氧化钝化电池的制备方法。背面采用抛光面的结构可有效的提升光利用率,采用一步沉积多晶硅磷掺杂及生长厚氧化掩膜层,减少了工艺步骤；然后进行绕镀整面去除,加大了工艺窗口,规避了目前常用的工艺流程是先正面硼扩散再背面多晶硅掺杂的弊端——绕镀去除的难度,然而即使去除干净,必然也会造成一定的印记,影响外观良率。同时本发明方法引入退火与硼掺杂二合一的方式,不仅简化了流程,同时无外观不良,工艺流程短,能耗少,有效的提高了生产良率和质量等特点。(The invention belongs to the field of solar photovoltaic industry, and particularly relates to a preparation method of a tunneling oxidation passivation battery. The back surface adopts a polished surface structure, so that the light utilization rate can be effectively improved, and the process steps are reduced by adopting one-step deposition of polysilicon phosphorus doping and thick oxidation mask layer growth; and then, the whole surface of the winding plating is removed, so that the process window is enlarged, the defect that the conventional process flow is that the front boron is diffused firstly and then the back polysilicon is doped, namely the difficulty of winding plating removal is overcome, and even if the process flow is completely removed, certain marks are inevitably caused, so that the appearance yield is influenced. Meanwhile, the method introduces a mode of combining annealing and boron doping, thereby simplifying the process, having no bad appearance, having short process flow and less energy consumption, effectively improving the production yield and quality and the like.)

1. A preparation method of a tunneling oxidation passivation battery is characterized by comprising the following steps: the preparation method comprises the following specific process steps:

(1) polishing of

Polishing treatment is carried out in a groove type/chain type KOH/NaOH & polishing additive mode;

(2) doped polysilicon

Performing tunneling oxidation and doped polysilicon deposition in an LPCVD tube furnace, and simultaneously growing a thick oxide layer on the surface to play a role of a mask;

(3) plating removal and texturing

Using water film protection and HF/HNO₃Etching the liquid medicine at low temperature or washing the liquid medicine in an alkali-washing chain manner, and removing the doped polycrystalline silicon wound and expanded to the reverse side; then, texturing is carried out;

(4) boron diffusion

Firstly, high-temperature annealing is carried out to form an N + layer with higher crystallization degree, and then gas-phase BCl is adopted₃Liquid phase BBr₃Or forming a P + layer in a spin coating mode;

(5) RCA cleaning

Removing BSG and PSG by using HF with the mass concentration of 1-5%, and then performing standard RCA cleaning to obtain a clean surface;

(6) passivation of

Growing alumina on the boron-doped surface by adopting an ALD (atomic layer deposition) mode; then, depositing silicon nitride on the front surface and the back surface in a PECVD (plasma enhanced chemical vapor deposition) mode;

(7) screen printing

And printing the grid line electrode by using a screen printing mode, and annealing the cell slice in a chain sintering furnace.

2. The method of claim 1, wherein the method comprises: the specific proportion of the polishing agent adopted in the polishing treatment in the step (1) is KOH/NaOH, polishing additive and H₂The volume ratio of O is 1:2:15-2:1:15, the temperature is controlled at 70-85 ℃, the polishing time is 5-8min, the thinning weight is 0.4-0.8g, and the reflectivity is controlled at 35-40%.

3. The method of claim 1, wherein the method comprises: the temperature of the tunneling oxidation deposition in the step (2) is maintained at 550-650 DEG C₂1-3L for 10-30min, and thickness of 1-2 nm; the doped polysilicon is deposited as: intrinsic polysilicon deposition is carried out in a tube type LPCVD furnace, the deposition temperature is 550 ℃ and 650 ℃ and SiH₄The flow rate is 400-; then SiH is introduced₄400-700sccm, pH of 1-5% mass concentration₃40-100sccm for 30-60min, and the thickness of doped polysilicon is 100-.

4. The method of claim 1, wherein the method comprises: the acid etching method adopted in the step (3) is HF/HNO (hydrogen fluoride/hydrogen sulfide) bleaching in water₃Etching with liquid medicine at low temperature of 15-18 deg.C, HF and HNO₃And H₂The volume ratio of O is controlled to be 1:8:13-1:15:15, and the time is 0.5-2 min; or 3-7% KOH with mass concentration by adopting a water film protection water floating mode, the temperature is 60-80 ℃, and the time is 0.5-1 min; the texturing is carried out by pre-cleaning for 2min in a chain machine with HCl and H₂O₂The volume ratio of (1: 3) to (1: 1) and the temperature is maintained at 70-85 ℃; and then quickly making the wool in a volume ratio of 6:1-10:1 of KOH to the quick wool making additive at the temperature of 75-85 ℃ for 1-3min, wherein the thinning amount is controlled to be 0.2-0.4 g.

5. The method of claim 4, wherein the method comprises: the rapid texturing additive comprises the following components in parts by weight: 3-8 parts of sodium lactate, 10-15 parts of surfactant, 1-2 parts of polyvinylpyrrolidone, 0.1-2 parts of carboxylate and 75-85 parts of deionized water.

6. The method of claim 1, wherein the method comprises: in the step (4), boron is diffused at 800-900 ℃ N₂Annealing at high temperature for 30-60min for 1-3L to form N + layer with high crystallization degree, and performing gas phase BCl₃:O₂1:1-1: 3/liquid phase BBr₃:O₂The P + layer was formed in 2:1 to 1:3 or spin coating.

7. The method of claim 1, wherein the method comprises: in the step (5), HCL and H are used in the standard RCA cleaning₂O₂The volume ratio of (1: 3) - (1: 1), 70-85 deg.C, 5-10 min; NH (NH)₃H₂O and H₂O₂The volume ratio of (1: 3) - (1: 1), 70-85 deg.C, 5-10min, and finally dehydrating with 2-7% mass concentration HF to obtain clean surface.

8. The method of claim 1, wherein the method comprises: the thickness of the aluminum oxide on the front side in the step (6) is controlled to be 2-10nm, the thickness of the silicon nitride on the front side and the back side is controlled to be 75-90nm, and the refractive index is 1.8-2.2.

9. The method of claim 1, wherein the method comprises: the annealing temperature in the step (7) is 700-800 ℃, and the time is 0.5-1 min.

Technical Field

The invention belongs to the field of solar photovoltaic industry, and particularly relates to a preparation method of a novel tunneling oxidation passivation battery.

Background

The pursuit of high-efficiency batteries is a development trend in the photovoltaic industry, and has a scheme of combining cost and process, the mainstream product is a PERC (passivated emitter rear surface fully diffused) battery at present, but the efficiency is a bottleneck, and a novel battery structure is introduced to carry out a through oxidation passivation contact battery. The structure provides good surface passivation for the back of the silicon chip, the ultrathin oxide layer can enable multi-electron tunneling to enter the polysilicon layer and simultaneously block minority hole recombination, and then electrons are transversely transmitted in the polysilicon layer and collected by metal, so that metal contact recombination current is greatly reduced, and open-circuit voltage and short-circuit current of a battery are improved. However, the technology has certain defects in mass production, namely, the plating is not cleaned completely, so that the appearance is influenced, and the efficiency of the battery piece is directly influenced.

The conventional process flow adopts the steps of firstly performing boron diffusion on the front side and then performing intrinsic polycrystalline silicon and phosphorus doping annealing on the back side step by step, thereby increasing the difficulty of winding plating to a certain extent, reducing the appearance yield of finished products, and having higher cost and narrower process window; for the mask layer process which is carried out step by step for protecting the boron doping of the front surface, a process flow is additionally added, the labor and equipment cost is increased, and the complexity of the process flow is increased. For the conventional winding plating cleaning process flow for protecting the polysilicon layer on the back, a step-by-step mode is required, firstly a single-side cleaning mode is carried out to remove the phosphorosilicate glass on the front, then the winding expanding polysilicon is cleaned and removed, and then the RCA cleaning is carried out, so that the process flow complexity is increased to a certain extent, and meanwhile, the labor cost and the equipment cost are increased.

Disclosure of Invention

The invention aims to solve the technical problems of long process flow and poor appearance of the winding plating cleaning in the prior art, and provides a novel preparation process of a tunneling oxidation passivation battery. And then, the whole surface of the coil plating is removed, and the annealing and boron doping two-in-one mode is adopted, so that the process flow is shortened, the investment of equipment cost is reduced, the coil plating appearance is not bad, the production yield and quality are effectively improved, and the like.

The technical purpose of the invention is realized by the following technical scheme: a preparation method of a novel tunneling oxidation passivation battery specifically comprises the following operations:

(1) polishing, namely polishing by adopting a groove type/chain type KOH/NaOH and polishing additive mode;

in the polishing treatment process: KOH/NaOH polishing additive: h₂O is 1:2:15-2:1:15 (volume ratio), the temperature is controlled at 70-85 ℃, the polishing time is 5-8min, the thinning weight is 0.4-0.8g, and the reflectivity is controlled at 35-40%;

the polishing additive comprises the following components in parts by weight: 1-5 parts of sodium benzoate, 3-9 parts of a surfactant (composed of sodium hydroxide and alkylphenol ethoxylates according to the mass ratio of 1:1-1: 3), 5-17 parts of palmitic acid, 1-4 parts of polyethylene glycol, 1-6 parts of alkyl polyglycoside and 60-85 parts of deionized water.

(2) Doping polysilicon-performing tunnel oxidation and doped polysilicon deposition (forming an N + layer in a tube LPCVD (low pressure vapor phase chemical deposition)) in an LPCVD tube furnace, and simultaneously growing a thick oxide layer on the surface to play a role of a mask and prevent high temperature boron doping from entering.

Performing tunnel oxidation in LPCVD tube furnace at deposition temperature of 550-650 deg.C₂1-3L (oxygen) for 10-30min, and thickness of 1-2 nm;

doped polysilicon deposition- -intrinsic polysilicon deposition is first carried out in a tubular LPCVD (low pressure vapor phase chemical deposition) furnace at a deposition temperature of 550-₄The flow rate of (silane) is 400-700sccm for 2-10 min; then SiH is introduced₄400-700sccm, 1-5% mass concentration (relative to N)₂) pH of (1)₃40-100sccm for 30-60min, and the thickness of doped polysilicon is 100-.

(3) Removing by plating and texturing-by water film protection, adopting HF/HNO₃The doped polysilicon wound to the reverse side is removed by liquid medicine low-temperature etching or alkali washing chain type cleaning, and the chain type scheme is adopted to protect the doped side from being damaged to a certain extentAnd is bad. A small double-suede structure is formed by adopting a chain type alkali texturing mode, and the scheme uses a quick texturing additive which has small corrosion on an oxide layer; the additive can be used for rapid texturing, the reaction time is only 1-3min, and carboxylate is contained to protect an oxide layer, so that the problems that the common texturing additive has longer reaction time of 4-8min, cannot form a good textured structure in a short time and has a destructive effect on the oxide layer are solved.

The quick texturing additive comprises the following components in parts by weight: 3-8 parts of sodium lactate, 10-15 parts of a surfactant (composed of sodium hydroxide and a polyether modified polysiloxane defoaming agent according to the mass ratio of 1:1-1: 3), 1-2 parts of polyvinylpyrrolidone, 0.1-2 parts of carboxylate and 75-85 parts of deionized water.

The acid etching method is to float HF/HNO on water₃Etching with the liquid at low temperature of 15-18 deg.C, HF/HNO₃/H₂The volume ratio of O is controlled to be 1:8:13-1:15:15, and the time is about 0.5-2 min; is rich in HNO unlike the conventional etching solution₃The system is mainly used for protecting the phosphorus doped polycrystalline junction from being damaged. Or by adopting a water film protection water floating mode, 3-7% of KOH with mass concentration is used, the temperature is 60-80 ℃, the time is 0.5-1min, and the spread doped polysilicon is quickly removed without damaging the surface of the phosphorus doped polysilicon.

The texturing is carried out by pre-cleaning for 2min in a chain machine with HCl (hydrogen chloride) and H₂O₂1:3-1:1 (volume ratio), and maintaining the temperature at 70-85 ℃; and then quickly making the wool in KOH and the quick wool making additive in a volume ratio of 6:1-10:1, maintaining the temperature at 75-85 ℃ and the time for about 1-3 min. The amount of the thin film is controlled to be 0.2-0.4 g.

(4) Boron diffusion-firstly carrying out high-temperature annealing to form an N + layer with higher crystallization degree, and then adopting gas-phase BCl₃Liquid phase BBr₃Or forming a P + layer in a spin coating mode;

firstly, in the furnace tube, at 800-₂Annealing at high temperature for 30-60min for 1-3L to form N + layer with high crystallization degree, and performing gas phase BCl₃:O₂1:1-1:3 (volume ratio)/liquid phase BBr₃:O₂(vol.) or spin-coated (0.4-0.7 mg) formulationsFormula (II) form a P + layer.

(5) RCA cleaning, namely removing BSG (borosilicate glass) and PSG (phosphosilicate glass) by using HF with the mass concentration of 1-5%, and then performing standard RCA (standard chemical cleaning) cleaning to obtain a cleaner surface;

wherein BSG and PSG are removed with 1-5% by mass HF, followed by standard RCA cleaning (HCL: H)₂O₂1:3-1:1 (volume ratio), 70-85 ℃, 5-10 min; NH (NH)₃H₂O:H₂O₂1:3-1:1 (volume ratio), 70-85 deg.C, 5-10 min. ) And finally, performing dehydration treatment by adopting HF with the mass concentration of 2-7% to obtain a cleaner surface.

(6) Passivation-adopting ALD mode to grow alumina on boron-doped surface, playing a good role in chemical passivation of fixed negative charges, controlling the thickness of alumina on front surface at 2-10nm, and utilizing PECVD mode to grow silicon nitride on front and back surfaces to play a role in surface field passivation. The thickness is controlled to be 75-90nm, and the refractive index is 1.8-2.2;

(7) and (4) silk-screen printing, namely, printing the grid line electrode by using a silk-screen printing mode, and annealing the cell slice in a chain sintering furnace.

The annealing temperature is 700 ℃ and 800 ℃, and the time is about 0.5-1 min.

Compared with the prior art, the invention has the beneficial effects that:

1. the polysilicon is doped with phosphorus first and then doped with boron, so that the appearance is completely poor, and the production yield is greatly improved;

2. the thick oxidation process is integrated in the phosphorus doped polysilicon process, so that a machine for manufacturing a mask is saved; and the cost is saved, and meanwhile, due to the thicker oxide layer, the heating is more uniform in the subsequent annealing process, so that the uniformity after doping is effectively improved.

3. The boron doping process integrates the annealing process of the phosphorus-doped polysilicon, namely, one annealing furnace is omitted, so that the process is simplified and the cost is saved; and high-temperature treatment is carried out, the phosphorus-doped microcrystalline silicon structure is converted into polycrystalline silicon as soon as possible, a PSG protective layer is generated, boron elements are prevented from entering the phosphorus-doped polycrystalline silicon, and meanwhile due to the high-temperature characteristic of the boron doping process, the impurity absorption effect of phosphorus doping of the polycrystalline silicon can be improved, and the passivation performance is further improved.

4. The plating removal and texturing process is integrated in one machine, so that the additional equipment investment is reduced, the cost is saved, and the flow is simplified. The process window is wide and is suitable for mass production.

Drawings

FIG. 1 is a schematic process flow diagram of a conventional tunneling oxidation passivated cell;

FIG. 2 is a schematic diagram of a process flow for tunnel oxidation passivation of a battery according to the present invention;

FIG. 3 is a schematic view of the process flow of phosphorus doping and mask layer separation in comparative example 1;

FIG. 4 is a schematic flow chart of a separate process for annealing and boron doping in comparative example 2;

FIG. 5 is a comparative illustration of the appearance improvement between the conventional flow and the flow of the present invention.

Detailed Description

The present invention will be described in further detail with reference to specific embodiments, but the scope of the present invention is not limited to the description.