EP2470619A1 - Additive for alkaline etching solutions, in particular for texture etching solutions, and process for producing it - Google Patents

Additive for alkaline etching solutions, in particular for texture etching solutions, and process for producing it

Info

Publication number
EP2470619A1
EP2470619A1 EP11727757A EP11727757A EP2470619A1 EP 2470619 A1 EP2470619 A1 EP 2470619A1 EP 11727757 A EP11727757 A EP 11727757A EP 11727757 A EP11727757 A EP 11727757A EP 2470619 A1 EP2470619 A1 EP 2470619A1
Authority
EP
European Patent Office
Prior art keywords
phase mixture
product
colour
etching
hydroxide
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.)
Withdrawn
Application number
EP11727757A
Other languages
German (de)
French (fr)
Inventor
Jens KRÜMBERG
Ihor Melnyk
Michael Michel
Michael Schmidt
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.)
GP Solar GmbH
Original Assignee
GP Solar 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 GP Solar GmbH filed Critical GP Solar GmbH
Publication of EP2470619A1 publication Critical patent/EP2470619A1/en
Withdrawn legal-status Critical Current

Links

Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L31/02—Details
    • H01L31/0236—Special surface textures
    • 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
    • C09K13/02—Etching, surface-brightening or pickling compositions containing an alkali metal hydroxide
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L31/02—Details
    • H01L31/0236—Special surface textures
    • H01L31/02363—Special surface textures of the semiconductor body itself, e.g. textured active layers

Definitions

  • the invention concerns a product, its use as an additive or component of etching solutions and a process for producing it.
  • etching materials When etching materials, the aim is frequently to obtain an etching result which is defined in terms of the type, position and/or extent of the etching. This is particularly the case when semiconductor materials are etched, for example in the manufacture of electronic components or solar cells.
  • semiconductor material is silicon.
  • monocrystalline or multicrystalline silicon is used as semiconductor material in the industrial manufacture of silicon solar cells.
  • a defined etching of crystalline materials, in particular monocrystalline or multicrystalline silicon, is expensive, since the different types of grains and any crystal defects present are etched to varying degrees by most etching solu- tions. This is the case, for example, with alkali hydroxide- based alkaline etching solutions, which are used on an industrial scale in the etching and in particular in the texture etching of silicon wafers.
  • the respective etching process must be precisely coordinated with the semiconductor material, for example silicon material, used in the individual case.
  • Etching parameters such as etching time, composition of the etching solution and etching temperature can thereby be influ- enced, inter alia, by the type of crystallisation of the semiconductor material used, e.g. block-cast or edge-stabilised drawn multicrystalline silicon or monocrystalline silicon, the dopant type and dopant thickness thereof and also the type and density of the crystal defects.
  • the result of this is that different etching parameters must be used in each case, even for the various silicon materials from a single manufacturer.
  • the multiplicity of etching parameters increases still more when materials from various manufacturers are used.
  • texture etchings such as those fre- quently carried out in the production of solar cells in order to form a surface structure for the purpose of increasing the injection of light
  • the sensitivity of the texture etching processes with respect to the material used gives rise to a large number of different sets of etching parameters.
  • DE 10 2008 056 086 discloses an additive for etching solutions which makes this possible.
  • the production of this additive requires the separation of phases of various densities, which is accompanied by a certain expense.
  • the present invention is therefore based on the problem of providing a product which enables the etching processes, espe- cially texture etching processes, to be simplified and can be produced at little expense.
  • the product according to the invention is obtainable by mixing at least one polyethylene glycol with a base, forming a single-phase mixture, heating the single-phase mixture to a temperature of 80°C and allowing the single-phase mixture to rest in ambient air until the single-phase mixture changes colour.
  • base in this case means, in principle, any compound and any element capable of forming hydroxide ions in aqueous solution.
  • the base used is an alkali hydroxide or an ammonium hydroxide, especially preferably potassium hydroxide or sodium hydroxide.
  • the mass fraction of the alkali hydroxide used, in the components mixed for the purpose of forming the single-phase mixture, for example tetraethylene glycol and potassium hydroxide, is 1 to 10 mass percent, preferably about 7 mass percent.
  • Single-phase mixture means that the mixture, even after a long service life of several hours, does not separate into several phases of varying density.
  • Ambient air in the present sense is a gas mixture, such as that usually found on the earth in ar ⁇ eas occupied by human beings.
  • the term ⁇ allow to rest' in this case does not necessarily mean an absolute rest of the mix- ture.
  • the mixture can also be moved.
  • a colour change of the single-phase mixture takes place when the single-phase mixture changes its colour with respect to its original colour.
  • there is a change of colour when a previously transparent single-phase mixture takes on a colour.
  • the resting time until the change of colour depends on many parameters, in particular the mixed substances. In most cases, a resting period of about 15 minutes to 16 hours is required .
  • the etching solution can be used for various types and qualities of a semiconductor material using the same etching parameters and with equivalent etching results, for example in the same way for p-doped as well as for n-doped silicon.
  • the number of etching parameter sets required known as etching recipes, can therefore be significantly reduced. This reduction in the number of etching recipes required further simplifies, insofar as this may even be necessary, the adaptation of both the composition of the etching solution and the etching parameters to the semiconductor material to be etched. Moreover, an extended service life of the etching solution may result.
  • both monocrystalline and multicrystalline semiconductor materials in particular silicon wafers
  • aqueous texture etching solutions which contain 0.5 to 6 wt . % in alkali hydroxides and 1 to 10% by volume of alcohols, mostly isopropyl alcohol (cf. e.g. US 3,998,659) are used as texture etching solutions.
  • the texture etching usually takes place at a temperature of 70 to 90°C over a period of typically 20 to 75 minutes.
  • the single-phase mixture is allowed to rest in ambient air until it takes on a colour which lies between orange and red-brown in the optical spectrum.
  • the single-phase mixture is allowed to rest until it takes on a red-brown shade. It has emerged that the darker the shade to which the product according to the invention changes, the more effective it is. An especially strong effect results when the shade is red-brown. However, from a certain degree of colour change, the effect of the product reduces again. So when the single-phase mixture is dark brown or black, there is only a weak effect.
  • One variant embodiment of the invention makes provision for the at least one polyethylene glycol to be mixed with the base and water to form the single-phase mixture.
  • aqueous alkali hydroxide solution with the at least one polyethylene glycol.
  • aqueous alkali hydroxide solutions with an alkali, hydroxide concentration of at least 20 mass percent have been proven for this.
  • the water proportion must always be selected such that a single-phase mixture is formed and the mixture does not separate into several phases after a certain service life.
  • a non-oxidising acid is admixed into the single-phase mixture, preferably hydrochloric acid or acetic acid.
  • the product according to the invention is unstable over time with respect to its ef- feet.
  • stability and therefore storage life can be improved.
  • the product containing the non-oxidising acid can thus be stored for longer. It has proven advantageous to admix the non-oxidising acid in such a way that a pH value of less then 7, preferably less than 3, ensues.
  • the non-oxidising acid is admixed after the single-phase mixture has changed colour.
  • water and at least one alkali hydroxide preferably sodium hydroxide or potassium hydroxide
  • an etching or texture etching solution can be made available which is advantageous in one of the ways described above.
  • the proportion by volume of. the sin- gle-phase mixture in the mixture formed amounts to about 0.01 to 5%, preferably 0.01 to 1% and especially preferably 0.07 to 0.3%.
  • alcohol in particular isopropyl alcohol
  • the solution formed in the way de- scribed can in principle still be admixed with alcohol, in particular isopropyl alcohol.
  • All variant embodiments of the product according to the invention can be used advantageously as additive in alkaline etch- ing solutions for semiconductor materials, preferably in alkaline etching solutions for inorganic semiconductor materials such as monocrystalline or multicrystalline silicon. In particular they have proven advantageous as additive in texture etching solutions.
  • the product according to the invention can itself be used as texture etching solution for semiconductor materials, preferably for inorganic semiconductor materials and especially preferably for silicon materials such as monocrystalline or multicrystalline silicon wafers.
  • a surface texturing with randomly oriented pyramids can be produced on silicon surfaces. This has proven , itself especially on monocrystalline silicon surfaces.
  • the height of the pyramids in this case can be influenced by the ratio of the single-phase mixture to the texture etching solution used.
  • At least one polyethylene glycol is mixed with a base to form a single-phase mixture and a change in colour of the single-phase mixture is awaited.
  • base single-phase mixture and colour change are to be understood in the way explained above.
  • the change of colour takes place, for example, when the single-phase mixture is exposed to ambient air during the waiting period. In principle, however, other ambient atmospheres are also possible, provided they enable the necessary change in colour of the single-phase mixture. It is also possible to pass ambient air or other gas mixtures into or through the single-phase mixture, thus reducing the waiting period.
  • the at least one polyethylene glycol is mixed with the base and water to form the single-phase mixture.
  • This is done preferably by mixing the at least one polyethylene glycol with an aqueous solution of the base, for example with an aqueous sodium hydroxide or potassium hydroxide solution.
  • the proportion of water is, as described above, to be selected in such a way that the single-phase mixture does not separate into several phases.
  • Alkali hydroxides, in particular sodium hydroxide or potassium hydroxide have proven themselves as base.
  • the alkali hydroxide used or the mixture of several alkali hydroxides used is dosed in such a way that its mass fraction in the components mixed to form the single-phase mixture amounts to 1% to 10%, preferably about 7%.
  • a change of colour of the single-phase mixture is awaited, into a shade which lies between orange and red-brown in the optical spectrum.
  • the shade taken on by the single-phase mixture has an influence on its effect. Therefore it is preferable to wait for a change of colour into a red-brown shade, since a single-phase mixture which has changed colour in this way exhibits an espe- cially strong effect.
  • One advantageous variant embodiment of the process according to the invention provides that the single-phase mixture is heated to a temperature of at least 40°C, preferably to a tem- perature of between 40°C and 120°C and especially preferably to a temperature of between 75°C and 85°C.
  • a heating device used to heat the single-phase mixture is preferably turned off after the target temperature is reached, but can in principle also remain switched on while awaiting the colour change.
  • One refinement of the invention makes provision that a non- oxidising acid is admixed into the single-phase mixture, preferably hydrochloric acid or acetic acid.
  • a non- oxidising acid is admixed into the single-phase mixture, preferably hydrochloric acid or acetic acid.
  • the product which is unstable over time with respect to its effect can be stabilised and hence its storage life improved.
  • the admixture of acid takes place after the change of colour of the single-phase mixture. It has proven advantageous to ad ⁇ mix the acid in a concentration and quantity such that a pH value of the single-phase mixture of less than 7, preferably less than 3, ensues.
  • DE 10 2008 056 086 can likewise be stabilised by the admixture of a non-oxidising acid.
  • a product obtainable by mixing at least one polyethylene glycol with a base, allowing the mixture to rest in ambient air and at a temperature of about 25°C until two phases form and separating the less dense phase representing the product can thus be stabilised with respect to its effect by admixing a non-oxidising acid into the separated less dense phase, preferably hydrochloric acid or acetic acid.
  • the acid is preferably admixed in such a way that a pH value of the product of less than 7, preferably less than 3, ensues.
  • This described stabilisation by the admixture of a non- oxidising acid such as hydrochloric acid or acetic acid is compatible with all the refinements and variant embodiments of the product described in DE 10 2008 056 086, as well as with the production processes of the product and its application described therein and has proven to be advantageous. It has proven particularly advantageous in conjunction with the use of an alkali hydroxide, preferably sodium hydroxide or potas ⁇ sium hydroxide, as base, the use of tetraethylene glycol as at least one polyethylene glycol or the admixture of water into the mixture described in said application.
  • an alkali hydroxide preferably sodium hydroxide or potas ⁇ sium hydroxide
  • the admixture of a non-oxidising acid has also proven to be advantageous when water and alkali hydroxides, preferably sodium hydroxide or potassium hydroxide, are admixed into the separated less dense phase, in order thus to form a texture etching solution.
  • alkali hydroxides preferably sodium hydroxide or potassium hydroxide
  • the additional admixture of alcohol, pref ⁇ erably isopropyl alcohol, is compatible with the described admixture of non-oxidising acid.
  • such an admixture of alcohols is omitted, in order to avoid the associated disadvantages.
  • DE 10 2008 056 086 provides that at least one polyethylene glycol is mixed with a base, and after forming two phases in the resulting mixture, the less dense phase representing the product is separated and a non-oxidising acid, preferably hy ⁇ drochloric acid or acetic acid, is admixed into the separated phase.
  • a non-oxidising acid preferably hy ⁇ drochloric acid or acetic acid
  • a change of colour of the separated less dense phase into a shade which lies between orange and red-brown in the optical spectrum, for example an orange shade or a red- brown shade, is awaited.
  • the non-oxidising acid in this case is preferably admixed following the change of colour of the less dense phase.
  • Figure 1 Schematic view of the production of one embodiment of the product according to the invention
  • Figure 2 Schematic view of one embodiment of the process ac ⁇ cording to the invention
  • Figure 3 Illustration of individual steps of the embodiments from Figures 1 and 2
  • FIG. 1 shows the production of one embodiment of the product according to the invention in schematic view.
  • tetraethylene glycol is used as the at least one poly- ethylene glycol and potassium hydroxide (KOH) is used as base.
  • KOH potassium hydroxide
  • These components are mixed 10 to form a single-phase mixture.
  • the single-phase mixture in this case is heated 12 to 80°C.
  • the single-phase mixture is allowed to rest 14 until it has changed colour to a red-brown shade, i.e. has taken on a red-brown shade.
  • the single- phase mixture is allowed to rest in ambient air 14.
  • the heat supply in the present embodiment is stopped once the target temperature of 80°C is reached, so the single-phase mixture cools down during the resting period 14.
  • a change of colour of the single-phase mixture into a red-brown shade occurs after
  • FIG. 2 shows a schematic embodiment of the process according to the invention.
  • the starting point of the process in Figure 2 is tetraethylene glycol and an aqueous sodium hydroxide solution (NaOH solution) , which are firstly mixed together 20 to form a single-phase mixture.
  • the resulting mixture is heated to a temperature of at least 40°C 22, preferably to a temperature of between 40°C and 120°C and especially preferably to a temperature of between 75°C and 85°C.
  • a change of colour of the single-phase mixture to a red-brown shade is awaited 24. This typically takes place during a waiting period of 15 minutes to 16 hours.
  • Figure 3 is a schematic illustration of individual steps of the embodiments in Figure 1 and in Figure 2. So Figure 3 shows the single-phase mixture 52 arranged in a container 50 being heated 12 or 22 using a heating device 54.
  • the single-phase mixture 52 in the embodiments in Figures 1 and 2 is at first transparent, but after being left to rest 14, or waiting 24, it takes on a colour, in particular the red-brown shade known from Figures 1 and 2, so that a single-phase mixture 56 which has changed colour is present.
  • hydrochloric acid is admixed 26 into the single-phase mixture from Figure 1 or Figure 2, after being left to rest 14, or after awaiting the change of colour 24.
  • the stability of the product produced can be improved, so that it can be stored for longer.
  • Figure 5 shows a further refinement option for the embodiments from Figures 1 and 2 and also from Figure 4 in schematic view. According to this, the process steps in Figures 1, 2 or 4 are followed by an additional step of the admixture 28 of at least one alkali hydroxide and water to the single-phase mixture.
  • the resulting product can be used as etching solution, in particular as a texture etching solution, and has proven itself in texture etchings of silicon materials.
  • An etching solution of this type has been especially proven in the texture etching of monocrystalline silicon wafers.
  • NaOH or KOH are used as the at least one alkali hydroxide, in which case the at least one alkali hydroxide can be selected independently of the base used in the single-phase mixture 52.
  • a proportion by volume of 0.01% to 5% of the single- phase mixture to the mixture formed has proven itself.
  • this proportion by volume of the single-phase mixture amounts to 0.01 to 1% and especially preferably 0.07 to 0.3%.

Landscapes

  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Microelectronics & Electronic Packaging (AREA)
  • General Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Computer Hardware Design (AREA)
  • Physics & Mathematics (AREA)
  • Power Engineering (AREA)
  • Condensed Matter Physics & Semiconductors (AREA)
  • Materials Engineering (AREA)
  • Organic Chemistry (AREA)
  • Weting (AREA)
  • Photovoltaic Devices (AREA)
  • Cleaning Or Drying Semiconductors (AREA)

Abstract

Product (56) obtainable by mixing (10; 20) at least one polyethylene glycol with a base to form a single-phase mixture (52), heating (12; 22) of the single-phase mixture (52) to a temperature of 80°C and allowing the single-phase mixture (52) to rest (14) in ambient air until the single-phase mixture (52) changes colour, and also a process for the production of the product (56) and use of the product (56).

Description

Additive for alkaline etching solutions , in particular for texture etching solutions, and process for producing it
The invention concerns a product, its use as an additive or component of etching solutions and a process for producing it.
When etching materials, the aim is frequently to obtain an etching result which is defined in terms of the type, position and/or extent of the etching. This is particularly the case when semiconductor materials are etched, for example in the manufacture of electronic components or solar cells. The most commonly used semiconductor material is silicon. In particular, monocrystalline or multicrystalline silicon is used as semiconductor material in the industrial manufacture of silicon solar cells.
A defined etching of crystalline materials, in particular monocrystalline or multicrystalline silicon, is expensive, since the different types of grains and any crystal defects present are etched to varying degrees by most etching solu- tions. This is the case, for example, with alkali hydroxide- based alkaline etching solutions, which are used on an industrial scale in the etching and in particular in the texture etching of silicon wafers. Although it is possible to use other etching solutions, which etch the semiconductor materi- als evenly, regardless of the crystal orientation and crystal defects, their use on an industrial scale is problematic and expensive, mostly for reasons of safety or disposal, so that despite the anisotropic etching effect, alkaline etching solu¬ tions based on alkali hydroxides are frequently preferred.
In order to achieve a defined etching result with alkaline etching solutions of this type, the respective etching process must be precisely coordinated with the semiconductor material, for example silicon material, used in the individual case. Etching parameters such as etching time, composition of the etching solution and etching temperature can thereby be influ- enced, inter alia, by the type of crystallisation of the semiconductor material used, e.g. block-cast or edge-stabilised drawn multicrystalline silicon or monocrystalline silicon, the dopant type and dopant thickness thereof and also the type and density of the crystal defects. In practice, the result of this is that different etching parameters must be used in each case, even for the various silicon materials from a single manufacturer. The multiplicity of etching parameters increases still more when materials from various manufacturers are used. Especially in the case of texture etchings, such as those fre- quently carried out in the production of solar cells in order to form a surface structure for the purpose of increasing the injection of light, the sensitivity of the texture etching processes with respect to the material used gives rise to a large number of different sets of etching parameters.
Against this background, there is a need for simplification of the etching processes, in particular of texture etching processes. DE 10 2008 056 086 discloses an additive for etching solutions which makes this possible. The production of this additive requires the separation of phases of various densities, which is accompanied by a certain expense.
The present invention is therefore based on the problem of providing a product which enables the etching processes, espe- cially texture etching processes, to be simplified and can be produced at little expense.
This problem is solved by a product obtained in the manner ex¬ plained in claim 1. The invention is also based on the problem of providing a process for the production of this product. This problem is solved by a process with the features of claim 10.
Advantageous refinements in each case form the subject matter of dependent sub-claims.
Claims 8 and 9 concern advantageous applications of the product according to the invention.
The product according to the invention is obtainable by mixing at least one polyethylene glycol with a base, forming a single-phase mixture, heating the single-phase mixture to a temperature of 80°C and allowing the single-phase mixture to rest in ambient air until the single-phase mixture changes colour. The term base in this case means, in principle, any compound and any element capable of forming hydroxide ions in aqueous solution. For preference, the base used is an alkali hydroxide or an ammonium hydroxide, especially preferably potassium hydroxide or sodium hydroxide. The mass fraction of the alkali hydroxide used, in the components mixed for the purpose of forming the single-phase mixture, for example tetraethylene glycol and potassium hydroxide, is 1 to 10 mass percent, preferably about 7 mass percent.
Single-phase mixture means that the mixture, even after a long service life of several hours, does not separate into several phases of varying density. Ambient air in the present sense is a gas mixture, such as that usually found on the earth in ar¬ eas occupied by human beings. The term ^allow to rest' in this case does not necessarily mean an absolute rest of the mix- ture. In principle the mixture can also be moved. A colour change of the single-phase mixture takes place when the single-phase mixture changes its colour with respect to its original colour. In particular, there is a change of colour when a previously transparent single-phase mixture takes on a colour. The resting time until the change of colour depends on many parameters, in particular the mixed substances. In most cases, a resting period of about 15 minutes to 16 hours is required .
In principle, all polyethylene glycols can be used for the production of the product. In practice, the use of tetra- ethylene glycol has been proven. When this polyethylene glycol is used, for example, a resting period of about 15 minutes to 16 hours is required before the change of colour occurs.
It has emerged that admixing the product according to the invention into alkaline etching solutions, in particular into texture etching solutions, can have an advantageous effect on the etching processes. So, as the result of the admixture, the etching solution can be used for various types and qualities of a semiconductor material using the same etching parameters and with equivalent etching results, for example in the same way for p-doped as well as for n-doped silicon. The number of etching parameter sets required, known as etching recipes, can therefore be significantly reduced. This reduction in the number of etching recipes required further simplifies, insofar as this may even be necessary, the adaptation of both the composition of the etching solution and the etching parameters to the semiconductor material to be etched. Moreover, an extended service life of the etching solution may result.
If the product according to the invention is admixed into alkaline texture etching solutions, further advantages may also result. For example, both monocrystalline and multicrystalline semiconductor materials, in particular silicon wafers, can be textured using the same etching solution and identical etching parameters. In the state of the art, for example for silicon wafers, aqueous texture etching solutions which contain 0.5 to 6 wt . % in alkali hydroxides and 1 to 10% by volume of alcohols, mostly isopropyl alcohol (cf. e.g. US 3,998,659) are used as texture etching solutions. In this case, the texture etching usually takes place at a temperature of 70 to 90°C over a period of typically 20 to 75 minutes. When the product according to the invention is admixed into alcohol-containing alkaline etching solutions, it has emerged that the etching time can be reduced as a result and furthermore the amount of alcohol used in the alkaline etching solution can be reduced. It has also emerged that the alcohol consumption can not only be reduced, but the use of alcohol, in particular isopropyl alcohol, can be omitted altogether. It is therefore especially preferable, when using the product according to the invention as additive, to omit the admixture of alcohols completely.
In the case of semiconductor materials separated from a block by means of a sawing process, for example silicon wafers sepa¬ rated by means of an annular or a wire saw from. a silicon block, it is often necessary firstly to remove the saw damage by a separate, saw damage etching process, conducted in advance, before a texturing with structures with dimensions in the micron range can be reliably applied by means of a texture etching solution. When the product according to the invention is admixed into the texture etching solution, however, the separate saw damage etching process can be dispensed with and the etching of the saw damage can be conducted in a joint process step together with the texturing of the surface of the semiconductor material. The advantageous effects described are not reliant on the same bases being used for the production of the product according to the invention and in the alkaline etching solution. For example, sodium hydroxide can be used for the production of the product according to the invention, but the product can then be admixed into a solution containing potassium hydroxide.
In one refinement of the invention, the single-phase mixture is allowed to rest in ambient air until it takes on a colour which lies between orange and red-brown in the optical spectrum. Preferably the single-phase mixture is allowed to rest until it takes on a red-brown shade. It has emerged that the darker the shade to which the product according to the invention changes, the more effective it is. An especially strong effect results when the shade is red-brown. However, from a certain degree of colour change, the effect of the product reduces again. So when the single-phase mixture is dark brown or black, there is only a weak effect. One variant embodiment of the invention makes provision for the at least one polyethylene glycol to be mixed with the base and water to form the single-phase mixture. This is preferably done by mixing an aqueous alkali hydroxide solution with the at least one polyethylene glycol. In practice, aqueous alkali hydroxide solutions with an alkali, hydroxide concentration of at least 20 mass percent have been proven for this. The water proportion must always be selected such that a single-phase mixture is formed and the mixture does not separate into several phases after a certain service life.
In one refinement of the invention, a non-oxidising acid is admixed into the single-phase mixture, preferably hydrochloric acid or acetic acid. As mentioned above, the product according to the invention is unstable over time with respect to its ef- feet. As it has emerged, by admixing a non-oxidising acid as described, stability and therefore storage life can be improved. The product containing the non-oxidising acid can thus be stored for longer. It has proven advantageous to admix the non-oxidising acid in such a way that a pH value of less then 7, preferably less than 3, ensues. The non-oxidising acid is admixed after the single-phase mixture has changed colour.
In one advantageous variant embodiment, water and at least one alkali hydroxide, preferably sodium hydroxide or potassium hydroxide, are admixed into the single-phase mixture after it has changed colour. In this way an etching or texture etching solution can be made available which is advantageous in one of the ways described above. The proportion by volume of. the sin- gle-phase mixture in the mixture formed amounts to about 0.01 to 5%, preferably 0.01 to 1% and especially preferably 0.07 to 0.3%. As mentioned above, it was formerly the usual practice to admix alcohol, in particular isopropyl alcohol, into etching solutions of this type. The solution formed in the way de- scribed can in principle still be admixed with alcohol, in particular isopropyl alcohol. As explained above, however, lesser quantities are required. As a result of the use of the single-phase mixture, however, the alcohol which was formerly usually admixed can also be completely replaced by the single- phase mixture. Therefore it is especially preferable to omit an admixture of alcohols.
All variant embodiments of the product according to the invention can be used advantageously as additive in alkaline etch- ing solutions for semiconductor materials, preferably in alkaline etching solutions for inorganic semiconductor materials such as monocrystalline or multicrystalline silicon. In particular they have proven advantageous as additive in texture etching solutions. In the variant embodiment described, with admixed water and at least one alkali hydroxide, the product according to the invention can itself be used as texture etching solution for semiconductor materials, preferably for inorganic semiconductor materials and especially preferably for silicon materials such as monocrystalline or multicrystalline silicon wafers. For example, with this variant embodiment a surface texturing with randomly oriented pyramids can be produced on silicon surfaces. This has proven , itself especially on monocrystalline silicon surfaces. The height of the pyramids in this case can be influenced by the ratio of the single-phase mixture to the texture etching solution used.
In the process according to the invention for the production of the product, at least one polyethylene glycol is mixed with a base to form a single-phase mixture and a change in colour of the single-phase mixture is awaited. The terms base, single-phase mixture and colour change are to be understood in the way explained above. The change of colour takes place, for example, when the single-phase mixture is exposed to ambient air during the waiting period. In principle, however, other ambient atmospheres are also possible, provided they enable the necessary change in colour of the single-phase mixture. It is also possible to pass ambient air or other gas mixtures into or through the single-phase mixture, thus reducing the waiting period.
In one variant embodiment of the process according to the in- vention, the at least one polyethylene glycol is mixed with the base and water to form the single-phase mixture. This is done preferably by mixing the at least one polyethylene glycol with an aqueous solution of the base, for example with an aqueous sodium hydroxide or potassium hydroxide solution. The proportion of water is, as described above, to be selected in such a way that the single-phase mixture does not separate into several phases. Alkali hydroxides, in particular sodium hydroxide or potassium hydroxide, have proven themselves as base. Advantageously, the alkali hydroxide used or the mixture of several alkali hydroxides used, is dosed in such a way that its mass fraction in the components mixed to form the single-phase mixture amounts to 1% to 10%, preferably about 7%.
In one preferred variant embodiment of the process according to the invention, a change of colour of the single-phase mixture is awaited, into a shade which lies between orange and red-brown in the optical spectrum. As already explained above, the shade taken on by the single-phase mixture has an influence on its effect. Therefore it is preferable to wait for a change of colour into a red-brown shade, since a single-phase mixture which has changed colour in this way exhibits an espe- cially strong effect.
One advantageous variant embodiment of the process according to the invention provides that the single-phase mixture is heated to a temperature of at least 40°C, preferably to a tem- perature of between 40°C and 120°C and especially preferably to a temperature of between 75°C and 85°C. A heating device used to heat the single-phase mixture is preferably turned off after the target temperature is reached, but can in principle also remain switched on while awaiting the colour change.
One refinement of the invention makes provision that a non- oxidising acid is admixed into the single-phase mixture, preferably hydrochloric acid or acetic acid. As explained above, the product which is unstable over time with respect to its effect can be stabilised and hence its storage life improved. The admixture of acid takes place after the change of colour of the single-phase mixture. It has proven advantageous to ad¬ mix the acid in a concentration and quantity such that a pH value of the single-phase mixture of less than 7, preferably less than 3, ensues.
It has emerged that the product disclosed by
DE 10 2008 056 086 can likewise be stabilised by the admixture of a non-oxidising acid. A product obtainable by mixing at least one polyethylene glycol with a base, allowing the mixture to rest in ambient air and at a temperature of about 25°C until two phases form and separating the less dense phase representing the product can thus be stabilised with respect to its effect by admixing a non-oxidising acid into the separated less dense phase, preferably hydrochloric acid or acetic acid. The acid is preferably admixed in such a way that a pH value of the product of less than 7, preferably less than 3, ensues. This described stabilisation by the admixture of a non- oxidising acid such as hydrochloric acid or acetic acid is compatible with all the refinements and variant embodiments of the product described in DE 10 2008 056 086, as well as with the production processes of the product and its application described therein and has proven to be advantageous. It has proven particularly advantageous in conjunction with the use of an alkali hydroxide, preferably sodium hydroxide or potas¬ sium hydroxide, as base, the use of tetraethylene glycol as at least one polyethylene glycol or the admixture of water into the mixture described in said application.
The admixture of a non-oxidising acid has also proven to be advantageous when water and alkali hydroxides, preferably sodium hydroxide or potassium hydroxide, are admixed into the separated less dense phase, in order thus to form a texture etching solution. The additional admixture of alcohol, pref¬ erably isopropyl alcohol, is compatible with the described admixture of non-oxidising acid. Preferably, however, such an admixture of alcohols is omitted, in order to avoid the associated disadvantages.
One refinement of the production process described in
DE 10 2008 056 086 provides that at least one polyethylene glycol is mixed with a base, and after forming two phases in the resulting mixture, the less dense phase representing the product is separated and a non-oxidising acid, preferably hy¬ drochloric acid or acetic acid, is admixed into the separated phase.
Advantageously, a change of colour of the separated less dense phase into a shade which lies between orange and red-brown in the optical spectrum, for example an orange shade or a red- brown shade, is awaited. The non-oxidising acid in this case is preferably admixed following the change of colour of the less dense phase.
The invention will next be explained in more detail with the aid of the figures. Elements which have the same effect, inso- far as useful, have been given the same reference numbers. The figures show:
Figure 1 Schematic view of the production of one embodiment of the product according to the invention Figure 2 Schematic view of one embodiment of the process ac¬ cording to the invention Figure 3 Illustration of individual steps of the embodiments from Figures 1 and 2
Figure 4 Refinement option for the embodiments from Figures
1 and 2 Figure 5 A further refinement option for the embodiments
from Figures 1, 2 and 4
Figure 1 shows the production of one embodiment of the product according to the invention in schematic view. In this embodiment, tetraethylene glycol is used as the at least one poly- ethylene glycol and potassium hydroxide (KOH) is used as base. These components are mixed 10 to form a single-phase mixture. • The single-phase mixture in this case is heated 12 to 80°C. Next the single-phase mixture is allowed to rest 14 until it has changed colour to a red-brown shade, i.e. has taken on a red-brown shade. In the embodiment in Figure 1, the single- phase mixture is allowed to rest in ambient air 14. The heat supply in the present embodiment is stopped once the target temperature of 80°C is reached, so the single-phase mixture cools down during the resting period 14. A change of colour of the single-phase mixture into a red-brown shade occurs after
10 to 120 minutes of the resting period 14. The change of colour of the single-phase mixture can be accelerated by continuing the supply of heat during the resting period 14, although the effect of the product according to the invention also di- minishes more quickly.
Figure 2 shows a schematic embodiment of the process according to the invention. The starting point of the process in Figure 2 is tetraethylene glycol and an aqueous sodium hydroxide solution (NaOH solution) , which are firstly mixed together 20 to form a single-phase mixture. The resulting mixture is heated to a temperature of at least 40°C 22, preferably to a temperature of between 40°C and 120°C and especially preferably to a temperature of between 75°C and 85°C. Next, a change of colour of the single-phase mixture to a red-brown shade is awaited 24. This typically takes place during a waiting period of 15 minutes to 16 hours.
The procedure according to the illustration in Figure 1 obvi-' ously represents a further embodiment of the process according to the invention, since during the resting period 14 a change of colour of the single-phase mixture to a red-brown shade is awaited. In corresponding fashion, a further embodiment of the product according to the invention can be produced with the process in Figure 2, provided the single-phase mixture within the meaning of the present invention is left to rest during the period 24 of awaiting the change of colour of the single- phase mixture.
Figure 3 is a schematic illustration of individual steps of the embodiments in Figure 1 and in Figure 2. So Figure 3 shows the single-phase mixture 52 arranged in a container 50 being heated 12 or 22 using a heating device 54. The single-phase mixture 52 in the embodiments in Figures 1 and 2 is at first transparent, but after being left to rest 14, or waiting 24, it takes on a colour, in particular the red-brown shade known from Figures 1 and 2, so that a single-phase mixture 56 which has changed colour is present.
Both in the embodiment from Figure 1 and in the embodiment from Figure 2, mixtures of one or more of any polyethylene glycols, in particular of tetraethylene glycol, with any alkali hydroxides or an aqueous solution of any alkali hydroxides can be used. In particular, the use of NaOH or an aqueous KOH solution is thus also possible. When aqueous solutions are used, as explained above, care must be taken with respect to the quantity of water, so that the mixture formed does not separate into several phases. Figure 4 illustrates in outline form a refinement of the product according to the invention in accordance with the embodiment from Figure 1, together with the process according to the invention in accordance with the embodiment from Figure 2. According to the illustration in Figure 4, hydrochloric acid is admixed 26 into the single-phase mixture from Figure 1 or Figure 2, after being left to rest 14, or after awaiting the change of colour 24. As explained above, in this way the stability of the product produced can be improved, so that it can be stored for longer.
Figure 5 shows a further refinement option for the embodiments from Figures 1 and 2 and also from Figure 4 in schematic view. According to this, the process steps in Figures 1, 2 or 4 are followed by an additional step of the admixture 28 of at least one alkali hydroxide and water to the single-phase mixture.
The resulting product can be used as etching solution, in particular as a texture etching solution, and has proven itself in texture etchings of silicon materials. An etching solution of this type has been especially proven in the texture etching of monocrystalline silicon wafers. For preference, NaOH or KOH are used as the at least one alkali hydroxide, in which case the at least one alkali hydroxide can be selected independently of the base used in the single-phase mixture 52. In practice, a proportion by volume of 0.01% to 5% of the single- phase mixture to the mixture formed has proven itself. Pref¬ erably, this proportion by volume of the single-phase mixture amounts to 0.01 to 1% and especially preferably 0.07 to 0.3%. List of reference numbers
10 mix tetraethylene glycol with potassium hydroxide (KOH) 12 heat single-phase mixture
14 single-phase mixture allowed to rest until it changes colour to red-brown shade
20 mix tetraethylene glycol with aqueous sodium hydroxide solution (NaOH solution)
22 heat single-phase mixture
24 wait for single-phase mixture to change colour to a red- brown shade
26 admixture of hydrochloric acid into single-phase mixture 28 admixture of at least one alkali hydroxide and water into . single-phase mixture
50 container
52 single-phase mixture
54 heating device
56 single-phase mixture after changing colour

Claims

Claims
1. Product (56) obtainable by
- mixing (10; 20) at least one polyethylene glycol with a base to form a single-phase mixture (52);
- heating (12; 22) the single-phase mixture (52) to a temperature of 80°C and
- allowing the single-phase mixture (52) to rest (14) in ambient air until the single-phase mixture (52) changes colour .
2. Product (56) according to claim 1,
c h a r a c t e r i s e d i n t h a t
an alkali hydroxide or an ammonium hydroxide is used as base (10; 20), preferably sodium hydroxide or potassium hydroxide .
3. Product (56) according to one of the preceding claims,
c h a r a c t e r i s e d i n t h a t
tetraethylene glycol is used as at least one polyethylene glycol (10; 20) .
4. Product (56) according to one of the preceding claims,
c h a r a c t e r i s e d i n t h a t
the single-phase mixture (52) is allowed to rest (14) in ambient air (14), until it takes on a shade which lies between orange and red-brown in the optical spectrum, preferably a red-brown shade.
5. Product (56) according to one of the preceding claims,
c h a r a c t e r i s e d i n t h a t
the at least one polyethylene glycol is mixed (20) with the base and water to form the single-phase mixture, preferably by mixing an aqueous alkali hydroxide solution with the at least one polyethylene glycol.
6. Product according to one of the preceding claims,
c h a r a c t e r i s e d i n t h a t
a non-oxidising acid is admixed into (26) the single-phase mixture (52), preferably hydrochloric acid or acetic acid.
7. Product according to one of the preceding claims,
c h a r a c t e r i s e d i n t h a t
after the single-phase mixture (56) has changed colour, wa ter and at least one alkali hydroxide, preferably sodium hydroxide or potassium hydroxide, are admixed into it.
8. Use of a product (56) according to one of claims 1 to 7 as additive in alkaline etching solutions for semiconductor materials, preferably in alkaline etching solutions for in organic semiconductor materials.
9. Use of a product according to claim 7 as texture etching solution for semiconductor materials, preferably for inorganic semiconductor materials and especially preferably for silicon.
10. Process for the production of a product (56) according to one of claims 1 to 7, in which
- a single-phase mixture is formed by mixing at least one polyethylene glycol with a base (10; 20) and
- a change in colour of the single-phase mixture is
awaited (14; 24) .
11. Process according to claim 10,
c h a r a c t e r i s e d i n t h a t an alkali hydroxide is used as base (10; 20), preferably sodium hydroxide or potassium hydroxide.
12. Process according to one of claims 10 to 11,
c h a r a c t e r i s e d i n t h a t
tetraethylene glycol is used as at least one polyethylene glycol (10; 20) .
13. Process according to one of claims 10 to 12,
c h a r a c t e r i s e d i n t h a t
a change of colour of the single-phase mixture (52) is awaited (14; 24) into a shade which lies between orange and red-brown in the optical spectrum, preferably into a red- brown shade.
14. Process according to one of claims 10 to 13,
c h a r a c t e r i s e d i n t h a t
the single-phase mixture (52) is heated to a temperature at least 40°C (12; 22), preferably to a temperature of between 40°C and 120°C and especially preferably to a temperature of between 75°C and 85°C.
15. Process according to one of claims 10 to 14,
c h a r a c t e r i s e d i n t h a t
a non-oxidising acid, preferably hydrochloric acid or acetic acid, is admixed (26) into the single-phase mixture (56).
EP11727757A 2010-04-30 2011-04-27 Additive for alkaline etching solutions, in particular for texture etching solutions, and process for producing it Withdrawn EP2470619A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE102010019079A DE102010019079A1 (en) 2010-04-30 2010-04-30 An additive for alkaline etching solutions, in particular for texture etching solutions, and process for its preparation
PCT/IB2011/000900 WO2011135435A1 (en) 2010-04-30 2011-04-27 Additive for alkaline etching solutions, in particular for texture etching solutions, and process for producing it

Publications (1)

Publication Number Publication Date
EP2470619A1 true EP2470619A1 (en) 2012-07-04

Family

ID=44358213

Family Applications (1)

Application Number Title Priority Date Filing Date
EP11727757A Withdrawn EP2470619A1 (en) 2010-04-30 2011-04-27 Additive for alkaline etching solutions, in particular for texture etching solutions, and process for producing it

Country Status (7)

Country Link
EP (1) EP2470619A1 (en)
JP (1) JP5632533B2 (en)
KR (1) KR101478892B1 (en)
CN (1) CN102695778B (en)
DE (1) DE102010019079A1 (en)
TW (1) TWI467054B (en)
WO (1) WO2011135435A1 (en)

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN102877135B (en) * 2012-09-07 2015-11-25 湖州三峰能源科技有限公司 Monocrystalline silicon piece alkalescence environment-friendly type is without the additive of alcohol Woolen-making liquid and using method thereof
TWI506122B (en) * 2012-09-20 2015-11-01 財團法人工業技術研究院 Etching composition and etching method for semiconductor wafer

Family Cites Families (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3998659A (en) 1974-01-28 1976-12-21 Texas Instruments Incorporated Solar cell with semiconductor particles and method of fabrication
US3909325A (en) * 1974-06-28 1975-09-30 Motorola Inc Polycrystalline etch
US5035809A (en) * 1990-10-05 1991-07-30 Eastman Kodak Company Dichloromethane abatement
US5536439A (en) * 1995-03-13 1996-07-16 Gage Products Company Non-abrasive line cleaning composition
DE19811878C2 (en) * 1998-03-18 2002-09-19 Siemens Solar Gmbh Process and etching solution for wet chemical pyramidal texture etching of silicon surfaces
JP2002322578A (en) * 2001-04-24 2002-11-08 Noritake Co Ltd Etching solution for aluminum thin film and method for forming aluminum thin pattern
DE102006051952A1 (en) * 2006-11-01 2008-05-08 Merck Patent Gmbh Particle-containing etching pastes for silicon surfaces and layers
SG166102A1 (en) * 2007-03-31 2010-11-29 Advanced Tech Materials Methods for stripping material for wafer reclamation
TW200842970A (en) * 2007-04-26 2008-11-01 Mallinckrodt Baker Inc Polysilicon planarization solution for planarizing low temperature poly-silicon thin filim panels
WO2009067475A1 (en) * 2007-11-19 2009-05-28 Applied Materials, Inc. Crystalline solar cell metallization methods
JP2011515872A (en) * 2008-03-25 2011-05-19 アプライド マテリアルズ インコーポレイテッド Surface cleaning and uneven formation process of crystalline solar cell
DE102008056086A1 (en) 2008-11-06 2010-05-12 Gp Solar Gmbh An additive for alkaline etching solutions, in particular for texture etching solutions and process for its preparation

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
See references of WO2011135435A1 *

Also Published As

Publication number Publication date
KR101478892B1 (en) 2015-01-05
JP5632533B2 (en) 2014-11-26
KR20130028730A (en) 2013-03-19
JP2013526050A (en) 2013-06-20
WO2011135435A1 (en) 2011-11-03
CN102695778B (en) 2015-10-21
TWI467054B (en) 2015-01-01
TW201211313A (en) 2012-03-16
CN102695778A (en) 2012-09-26
DE102010019079A1 (en) 2011-11-03

Similar Documents

Publication Publication Date Title
Chu et al. A simple and cost-effective approach for fabricating pyramids on crystalline silicon wafers
EP2891637B1 (en) Monocrystalline silicon wafer texturizing additive and use thereof
US9099582B2 (en) Silicon texturing formulations
US8329046B2 (en) Methods for damage etch and texturing of silicon single crystal substrates
CN103314449B (en) The method reversely etched for the wet-chemical of solar cell emitter
TWI573859B (en) Texture etching solution composition and texture etching method of crystalline silicon wafers (1)
US8440494B2 (en) Single-crystalline silicon alkaline texturing with glycerol or ethylene glycol additives
Wijekoon et al. Production ready noval texture etching process for fabrication of single crystalline silicon solar cells
WO2011135435A1 (en) Additive for alkaline etching solutions, in particular for texture etching solutions, and process for producing it
US20110260097A1 (en) Additive for alkaline etching solutions, in particular for texture etching solutions, and process for producing it
Damiani et al. Development of RIE-textured silicon solar cells
US20110180132A1 (en) Texturing and damage etch of silicon single crystal (100) substrates
TWI558791B (en) Chemical solutions for texturing multicrystalline silicon wafers for solar cell manufacturing
CN107924824B (en) Paste composition
TW201036058A (en) Solution for increasing wafer sheet resistance and/or photovoltaic cell power density level
US20150083209A1 (en) Coatable diffusing agent composition, method for producing coatable diffusing agent composition, solar cell, and method for manufacturing solar cell
CN114634766A (en) Additive for back polishing of monocrystalline silicon wafer and application thereof
Yoo et al. RIE surface texturing for optimum light trapping in multicrystalline silicon solar cells
Kong et al. Fabrication of silicon pyramid-nanocolumn structures with lowest reflectance by reactive ion etching method
Quiebras Wet chemical textures for crystalline silicon solar cells
WO2011081054A1 (en) Method for manufacturing a solar cell
Xiao et al. Morphology of etch-pits on HF-HNO3-H2O vapor-etched diamond wire sawn multi-crystalline silicon wafers
CN104278330A (en) Texturing liquid for crystalline silicon solar cell and preparation method thereof
Hajjiah et al. Study of surface morphology and optical characterization of crystalline and multi-crystalline silicon surface textured in highly diluted alkaline solutions
KR101863536B1 (en) Texture etching solution composition and texture etching method of crystalline silicon wafers

Legal Events

Date Code Title Description
PUAI Public reference made under article 153(3) epc to a published international application that has entered the european phase

Free format text: ORIGINAL CODE: 0009012

17P Request for examination filed

Effective date: 20120313

AK Designated contracting states

Kind code of ref document: A1

Designated state(s): AL AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HR HU IE IS IT LI LT LU LV MC MK MT NL NO PL PT RO RS SE SI SK SM TR

17Q First examination report despatched

Effective date: 20121004

RAP1 Party data changed (applicant data changed or rights of an application transferred)

Owner name: GP SOLAR GMBH

RIN1 Information on inventor provided before grant (corrected)

Inventor name: SCHMIDT, MICHAEL

Inventor name: KRUEMBERG, JENS

Inventor name: MICHEL, MICHAEL

Inventor name: MELNYK, IHOR

DAX Request for extension of the european patent (deleted)
RAP1 Party data changed (applicant data changed or rights of an application transferred)

Owner name: GP SOLAR GMBH

STAA Information on the status of an ep patent application or granted ep patent

Free format text: STATUS: EXAMINATION IS IN PROGRESS

STAA Information on the status of an ep patent application or granted ep patent

Free format text: STATUS: THE APPLICATION HAS BEEN WITHDRAWN

18W Application withdrawn

Effective date: 20170206