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WO2012142987A1 - Procédé de fabrication d'un substrat de silicium texturé - Google Patents

Procédé de fabrication d'un substrat de silicium texturé Download PDF

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Publication number
WO2012142987A1
WO2012142987A1 PCT/DE2012/000152 DE2012000152W WO2012142987A1 WO 2012142987 A1 WO2012142987 A1 WO 2012142987A1 DE 2012000152 W DE2012000152 W DE 2012000152W WO 2012142987 A1 WO2012142987 A1 WO 2012142987A1
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WO
WIPO (PCT)
Prior art keywords
silicon substrate
silicon
etching
catalyst solution
solution
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
Application number
PCT/DE2012/000152
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German (de)
English (en)
Inventor
Jakub Cichoszewski
Michael Reuter
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
SOVELLO GmbH
Original Assignee
SOVELLO GmbH
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by SOVELLO GmbH filed Critical SOVELLO GmbH
Publication of WO2012142987A1 publication Critical patent/WO2012142987A1/fr
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
    • C09K13/00—Etching, surface-brightening or pickling compositions
    • C09K13/04—Etching, surface-brightening or pickling compositions containing an inorganic acid
    • C09K13/08—Etching, surface-brightening or pickling compositions containing an inorganic acid containing a fluorine compound
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10F—INORGANIC SEMICONDUCTOR DEVICES SENSITIVE TO INFRARED RADIATION, LIGHT, ELECTROMAGNETIC RADIATION OF SHORTER WAVELENGTH OR CORPUSCULAR RADIATION
    • H10F77/00—Constructional details of devices covered by this subclass
    • H10F77/70—Surface textures, e.g. pyramid structures
    • H10F77/703—Surface textures, e.g. pyramid structures of the semiconductor bodies, e.g. textured active layers

Definitions

  • the invention relates to a method for producing a textured silicon substrate, in particular silicon wafer (Si wafer),
  • the light can escape from the solar cell again, without having created an electron-hole pair. This applies in particular to long-wave light. It is therefore desirable to reflect the light on the back instead of letting it escape unused.
  • the general aim of the invention is to reduce the reflection losses on the front side and to increase the reflection on the rear side in order to provide a method which significantly reduces the manufacturing costs.
  • From the prior art it is known to texturize silicon substrates in order to minimize reflection losses.
  • structures on the surface which have an angle of inclination of more than 30 °, there is the possibility that the reflected light hits the silicon surface a second time. Such structures are generally called texture.
  • the methods known from the prior art for producing a texture are manifold.
  • four process variants from the prior art are known for producing texturing, namely alkaline texturing on monocrystalline silicon, acid texturing of multicrystalline silicon, plasma texturing of multicrystalline silicon and texturing by selective etching removal by masks.
  • variants are known which expand the abovementioned processes by means of catalytic reactions.
  • alkaline texturing monocrystalline silicon is subjected to an alkaline etching step.
  • the ⁇ 1 1 1 ⁇ surfaces are attacked, which are inclined by 54.7 ° to the (10 O) direction.
  • the attack of the silicon surface can be carried out by bases such as potassium hydroxide or sodium hydroxide.
  • an aqueous solution of hydrofluoric acid, nitric acid and sulfuric acid or phosphoric acid is generally used for the etching.
  • Nitrogen oxides are formed in the reaction of silicon with nitric acid and hydrofluoric acid. Essentially, this gas bubble development leads to the thawing of the surface.
  • a big disadvantage of such etchings is the fast consumption during the etching process. This involves very high supply and disposal costs.
  • a further disadvantage is that the etching attack takes place on the front and rear side of the silicon wafer, as described, for example, in DE 103 20 212 A1. Thus, a reflection on the back is greatly reduced, which leads to optical losses in the long-wavelength range of light.
  • the isotropic etch attacks the multicrystalline wafers in particular at sites with a present crystal defect. Such sites are in particular so-called SAgeWarden, namely small cracks and cracks in the silicon crystal, which are caused by the sawing of silicon columns in the wafer.
  • the process of plasma etching proceeds in a vacuum atmosphere.
  • process gases such as SF 6 , CF 4 , Cl 2 or BC1 3 are used.
  • the disadvantage of these methods is the expensive vacuum technology and the non-corrosive design of the system. There is the possibility that the surface is damaged by high-energy particles from the plasma and recombination centers are generated. These cancel out the positive effect of texturing again.
  • Selective etching through a mask produces structures that resemble a honeycomb or inverted pyramids. These methods typically include a masking step, punctiform opening of the mask, subsequent etching and cleaning. Methods are known which mask with a SiN layer and open it with laser. The subsequent etching step is isotropic or anisotropic. By strong undercutting or a second etching step, the mask is removed.
  • first metal particles are deposited on the surface of a silicon wafer and then an etching of the surface of the silicon substrate takes place.
  • the deposited metal particles act as catalysts.
  • Such a method is described for example in DE 103 92 752 T5.
  • metal particles are deposited on the silicon substrate and then exposed to an etching process using hydrofluoric acid and hydrogen peroxide.
  • the surface of the silicon substrate is freed of native oxides.
  • the treatment of the silicon wafer is carried out by immersion in the catalyst solution or the etching solution.
  • the method described here has several disadvantages.
  • the treatment of the silicon wafer by immersion in the respective solutions and the resulting double-sided etching attack bring about optical losses.
  • the long process times of the etching step represent a serious disadvantage in these methods.
  • the additional step of initially cleaning the surface to remove native oxides seriously increases costs and process times.
  • the present invention has for its object to provide a method for producing a textured silicon substrate, in particular silicon wafer, which overcomes the disadvantages of the prior art.
  • This object is achieved by a method of the aforementioned type, comprising the following steps: a) one-sided application of an aqueous catalyst solution containing metal ions to the silicon substrate; b) treatment of the silicon substrate with an acidic and / or basic etching solution containing at least one oxidizing agent.
  • the inventive method has various advantages over the known methods. Due to the one-sided application of the aqueous catalyst solution to a silicon wafer, ie the localized, selective application of the catalyst solution will cause only one side of the silicon wafer to be textured in the subsequent etching step. Even if the silicon wafer is completely immersed in the etching solution during the etching step, only one side of the silicon wafer is etched, since etching is only carried out at the points at which metal particles in the form of metal clusters have deposited. This one-sided etching avoids a reduction of the reflection at the backside of the wafer, so that also optical losses in the long-wave range of the light are avoided.
  • the catalyst solution can also be applied only locally limited one-sided. In this way, z. B. can be achieved that is not textured under the busbars / fingers.
  • the method according to the invention makes it possible to texturize silicon wafers on one side when the silicon wafers are immersed over the entire area into the etching solution without masking step and without any special requirements for the etching apparatus.
  • the invention also enables isotropic texturing of silicon wafers independent of crystal orientation (including [1 1 l] crystal orientation) regardless of whether or not the surface has a sawing damage.
  • the metal ions contained in the catalyst solution deposit on the silicon surface as elemental metal nanoclusters.
  • silver eg AgNO 3
  • platinum eg H 2 PtCl 6
  • chromium copper or gold are conceivable.
  • the metal ions are palladium ions, the salt used preferably being PdCl 2 .
  • the salt used preferably being PdCl 2 .
  • PdCl 2 is particularly effective at depositing palladium ions onto a silicon surface. Also it was found out that
  • the catalyst solution contains HF.
  • the substrate is first immersed in an HF solution to remove native oxides and then treated on one side with the catalyst solution.
  • the metal particles usually adhere to the substrate surface after rinsing with water and a drying step.
  • non-standard silicon materials such as, for example, string-ribbon solar cells, are used in the method according to the invention.
  • HCl is also present in the catalyst solution containing metal ions.
  • the preferred palladium chloride HCl is required because palladium chloride is difficult to dissolve in water.
  • step a) both a removal of native oxides from the surface of the silicon substrate (either preferably by the HF-containing catalyst solution or by a prior treatment with HF) and a deposition of metal nanoparticles , in particular palladium nanoparticles, on the surface of the silicon substrate.
  • native oxide is meant such an oxide which forms when exposed to the silicon substrate of normal ambient air.
  • the catalyst solution is applied to the silicon substrate on one side by spraying, floating, overmolding, roller coating, slot die coating, sliding film die coating or knife coating.
  • the catalyst solution contains about 0.1 to 10% HF, about 0.1 to 10% HCl and about 1 mg to 100 mg / liter PdCl 2 .
  • the acid etching solution contains HF and / or NH 4 F and as oxidizing agent H 2 0 2 and / or HNO 3.
  • the substances mentioned have proven to be particularly effective in etching the silicon surface and are relatively unproblematic, especially in the disposal (in contrast to, for example, sulfuric acid or phosphoric acid).
  • the metal particles which precipitate out of the catalyst solution preferably have a size of 0.5 nm to 100 nm and preferably separate from one another at a distance of between 1 ⁇ m and 5 ⁇ m. These size and distance ratios ultimately achieve a particularly advantageous and effective etching of a silicon substrate.
  • a preferred process variant is characterized by a step c), in which the silicon substrate with an alkaline solution, preferably KOH solution, in particular a about 10% KOH solution is treated.
  • an alkaline solution preferably KOH solution, in particular a about 10% KOH solution
  • porous silicon which may be caused by unfavorable process conditions removed. Further, this alkaline solution etches anisotropically into the silicon material.
  • This step c) can then be followed by a neutralization step in which an acid (for example HCl) is used. This also removes metallic and organic contaminants from the wafer.
  • an acid for example HCl
  • Silicon substrate for a maximum of about 45 seconds, preferably about 30 to 35 seconds, the etching step b) exposed. This short etching time is a further advantage over the known prior art methods. Examples and results
  • a string-ribbon wafer with a thickness of 180 +/- 5 ⁇ and a size of 80 x 1 50 mm is treated on one side with an aqueous solution of hydrofluoric acid, hydrochloric acid and palladium chloride. Subsequently, a short etching step is carried out for 30 seconds in an acid solution of hydrofluoric acid (50%): nitric acid (69%): H 2 O (vol 4: 1: 2), whereby a porous silicon layer with a thickness of ⁇ 4 ⁇ arises.
  • hydrofluoric acid 50%): nitric acid (69%): H 2 O (vol 4: 1: 2)
  • the surface texture is formed by ablation of the porous silicon layer.
  • 1a) shows a scanning electron micrograph of the palladium nanoparticles with a size of 50 to 100 nm. After a treatment time of 30 seconds with a palladium chloride-containing catalyst solution, the elemental separates Palladium on the string-ribbon wafer from the palladium chloride solution with a cluster density of 1 0 cm " ab.
  • Fig. L b shows the string ribbon wafer after the above
  • the etching step forms a porous surface structure with pores having a diameter of less than 1 ⁇ m.
  • the palladium particles do not react directly with the silicon substrate or the etching solution, but sink into macropores, which are formed by the activated acid solution.
  • Figure lc shows the final texture morphology after a final potassium hydroxide treatment step.
  • the potassium hydroxide first removes the porous surface structure and then forms hemispherical recesses with a diameter of
  • Fig. 2 shows the reduction of the surface reflection R [%] of
  • the effective reflection R e ff is calculated by weighting the integrated reflection R (X) and the solar beam flux (N ph ) of an AM 1, 5G solar irradiation over a wavelength range from 400 nm to 1 000 nm.
  • the MAE texturing In particular, it reduces the reflection in the blue and red wavelength range.
  • the lower reflection for wavelengths ⁇ > 1 .000 nm indicates a higher degree of randomization of the irradiation and thus a longer light path in the material.
  • p-type doped string-ribbon wafers with a thickness of 1 80 +/- 5 ⁇ m and a size of 80 ⁇ 1 50 mm 2 were used.
  • a solution of hydrofluoric acid, hydrochloric acid and palladium chloride was used again.
  • the top porous silicon layer was removed by potassium hydroxide and the surface was restructured.
  • a treatment step followed by HCl followed by an RCA cleaning step to remove metallic and organic contaminants.
  • the wafers were subjected to a standard solar cell manufacturing process. A 60 ohms / sq. Emitter forms in a quartz glass furnace using POCL3.
  • An antireflection layer of silicon nitride having a layer thickness optimized on different surface morphologies is applied by means of PECVD.
  • the screen printing process applies the silver front metallization and the aluminum backside metallization.
  • the production of the solar cells is completed by firing and laser edge insulation.
  • T 25 ° C ISE corrected values) of 8 cells each from 2 groups, one group with MAE texture and one untextured reference group.
  • the mean open circuit voltage Voc remains about the same.
  • a small reduction in open circuit voltage is attributed to the increased surface area of the textured cells, while palladium contamination would result in a drastic reduction in Voc.
  • Quantum efficiency IQE shows a comparable electronic quality of the solar cells and stands for a comparable volume carrier lifetime.
  • the increased external quantum efficiency EQE of the MAE-textured cells for wavelengths ⁇ ⁇ 600nm results from the lower reflection of the front and leads to a higher
  • Short-circuit current density Jsc of AJsc +0.9 mA / cm 2 .
  • the same IQE in the wavelength range 700nm ⁇ ⁇ 1200nm proves the same material quality and also shows that there is no palladium contamination. Significant contamination with palladium would result in increased charge carrier recombination and thus reduced carrier lifetime.
  • the ribbon growth-on-substrate process also produces multicrystalline wafers without sawing damage.
  • the SLIVER and S I-GEN technologies produce monocrystalline wafers with [1 1 1] surface.
  • the MAE texture process is completely independent of crystal orientation due to the catalytically activated etching by metal particles and thus represents a significant simplification. Therefore, it is a good way to increase performance in all wafer processes mentioned above.

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  • Chemical & Material Sciences (AREA)
  • Inorganic Chemistry (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Organic Chemistry (AREA)
  • Weting (AREA)
  • Photovoltaic Devices (AREA)

Abstract

L'invention concerne un procédé de fabrication d'un substrat de silicium texturé, en particulier une tranche de silicium, comprenant les étapes de traitement suivantes consistant à : a) appliquer d'un côté une solution aqueuse de catalyseur contenant des ions métalliques, sur le substrat de silicium; b) traiter le substrat de silicium par une solution de gravure acide et/ou basique, contenant au moins un agent oxydant.
PCT/DE2012/000152 2011-04-18 2012-02-17 Procédé de fabrication d'un substrat de silicium texturé Ceased WO2012142987A1 (fr)

Applications Claiming Priority (6)

Application Number Priority Date Filing Date Title
EP11162859.0 2011-04-18
EP11162859 2011-04-18
DE102011017449 2011-04-18
DE102011017449.4 2011-04-18
DE102011115532A DE102011115532A1 (de) 2011-04-18 2011-10-11 Verfahren zur Herstellung eines texturierten Siliziumsubstrats
DE102011115532.9 2011-10-11

Publications (1)

Publication Number Publication Date
WO2012142987A1 true WO2012142987A1 (fr) 2012-10-26

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DE (1) DE102011115532A1 (fr)
WO (1) WO2012142987A1 (fr)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN112838140A (zh) * 2019-11-22 2021-05-25 阜宁阿特斯阳光电力科技有限公司 多晶硅太阳能电池及制备方法以及制备其绒面结构的方法

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN113930846A (zh) * 2021-12-15 2022-01-14 南京日托光伏新能源有限公司 匹配氢氧化钠单晶制绒方法

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE10320212A1 (de) 2003-05-07 2004-12-02 Universität Konstanz Verfahren zum Texturieren von Oberflächen von Silizium-Scheiben
DE10392752T5 (de) 2002-06-06 2005-06-02 Kansai Technology Licensing Organization Co., Ltd. Verfahren zur Herstellung eines multikristallinen Siliziumsubstrats für Solarzellen
US20100029034A1 (en) * 2007-10-24 2010-02-04 Mitsubishi Electric Corporation Method of manufacturing solar cell

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE10392752T5 (de) 2002-06-06 2005-06-02 Kansai Technology Licensing Organization Co., Ltd. Verfahren zur Herstellung eines multikristallinen Siliziumsubstrats für Solarzellen
DE10320212A1 (de) 2003-05-07 2004-12-02 Universität Konstanz Verfahren zum Texturieren von Oberflächen von Silizium-Scheiben
US20100029034A1 (en) * 2007-10-24 2010-02-04 Mitsubishi Electric Corporation Method of manufacturing solar cell

Non-Patent Citations (4)

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Title
HUANG Z ET AL: "Metal-Assisted Chemical Etching of Silicon: A Review", ADVANCED MATERIALS, WILEY VCH VERLAG, DE, vol. 23, no. 2, 11 January 2011 (2011-01-11), pages 285 - 308, XP002667196, ISSN: 0935-9648, [retrieved on 20100921], DOI: 10.1002/ADMA.201001784 *
MOHAMED L. CHOUROU ET AL: "Metal-assisted etching of p-type silicon under anodic polarization in HF solution with and without H2O2", ELECTROCHIMICA ACTA, vol. 55, no. 3, 1 January 2010 (2010-01-01), pages 903 - 912, XP055030509, ISSN: 0013-4686, DOI: 10.1016/j.electacta.2009.09.048 *
SHINJI YAE ET AL: "High Catalytic Activity of Palladium for Metal-Enhanced HF Etching of Silicon", JOURNAL OF THE ELECTROCHEMICAL SOCIETY, vol. 157, no. 2, 1 January 2010 (2010-01-01), pages D90 - D93, XP055030506, ISSN: 0013-4651, DOI: 10.1149/1.3264643 *
YOUN-JIN OH ET AL: "An In Situ ATR-FTIR Study on Palladium Displacement Reaction on Hydrogen-Terminated Silicon Surface", JOURNAL OF THE ELECTROCHEMICAL SOCIETY, vol. 152, no. 6, 1 January 2005 (2005-01-01), pages C348, XP055030703, ISSN: 0013-4651, DOI: 10.1149/1.1896326 *

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN112838140A (zh) * 2019-11-22 2021-05-25 阜宁阿特斯阳光电力科技有限公司 多晶硅太阳能电池及制备方法以及制备其绒面结构的方法
CN112838140B (zh) * 2019-11-22 2022-05-31 阜宁阿特斯阳光电力科技有限公司 多晶硅太阳能电池及制备方法以及制备其绒面结构的方法

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