Polishing solution for chip and preparation method thereof

Abstract

The invention discloses a polishing solution for a chip and a preparation method thereof.The polishing solution is prepared from, by weight, 0.5%-0.8% of modified abrasive, 1%-1.2% of hydrogen peroxide, 2%-2.5% of glycine, 0.1%-0.5% of modification inhibitor, 0.5%-1% of polyethylene glycol and the balance water, the raw materials are evenly mixed, potassium hydroxide is added to adjust the pH value to 8.5, the polishing solution for the chip is prepared, and the polishing solution for the chip is used for polishing the chip. A layer of compact passivation film can be formed on the copper surface by adding the modification inhibitor, corrosion of the polishing solution to the copper surface is effectively prevented, the modified filler takes silicon dioxide as a main body material, and aluminum oxide is embedded in the surface and the interior of the main body material, so that the modified filler is not easy to agglomerate while having high hardness, and the viscosity of the polishing solution is reduced; and therefore, the polishing liquid is easier to clean, the working procedures are reduced, and the polishing efficiency is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of chip polishing liquid preparation, and specifically relates to a polishing liquid for chips and a preparation method thereof. Background Art

[0002] With the continuous improvement of semiconductor manufacturing processes, chemical mechanical planarization (CMP) technology has become an indispensable key link in chip manufacturing. Traditional polishing methods often rely on physical friction, which easily leads to surface scratches or uneven wear. With the development of semiconductor technology, the requirements for the chip surface are getting higher and higher, and it is necessary to have higher flatness and as few defects as possible. The polishing liquid has become an important element for improving the chip surface. The existing polishing liquid uses alumina as an abrasive to improve the polishing efficiency. Although alumina has high hardness, its dispersion effect is poor, it is easy to agglomerate, and the surface cleaning after polishing is too complicated, increasing the cleaning process and reducing the polishing effect. Summary of the Invention

[0003] The purpose of the present invention is to provide a polishing liquid for chips and a preparation method thereof, which solves the problem that the polishing efficiency is not high due to the need for multiple cleaning after polishing with the current polishing liquid.

[0004] The purpose of the present invention can be achieved by the following technical solutions:

[0005] A preparation method of a polishing liquid for chips specifically includes the following steps:

[0006] Step A1: Mix octamethylcyclotetrasiloxane, tetramethyldisiloxane, tetramethylammonium hydroxide and dimethyl sulfoxide, introduce nitrogen protection, and react for 10 - 12 h under the conditions of a rotation speed of 120 - 150 r / min and a temperature of 90 - 95 °C to obtain dihydrogen polysiloxane;

[0007] Step A2: Mix 4-aminobenzotriazole, triethylamine and chloroform, stir and add acryloyl chloride under the conditions of a rotation speed of 150 - 200 r / min and a temperature of 0 °C, and react for 2 - 3 h to obtain a modifier. Mix the modifier, dihydrogen polysiloxane, chloroplatinic acid and N,N-dimethylformamide evenly, and react for 5 - 6 h under the conditions of a rotation speed of 120 - 150 r / min and a temperature of 70 - 80 °C to obtain a modified inhibitor;

[0008] Step A3: Weigh the following percentage of raw materials: 0.5 - 0.8% of modified abrasive, 1 - 1.2% of hydrogen peroxide, 2 - 2.5% of glycine, 0.1 - 0.5% of modified inhibitor and 0.5 - 1% of polyethylene glycol, and the balance is water. Mix the raw materials evenly, and add potassium hydroxide to adjust the pH value to 8.5 to obtain the polishing liquid for chips.

[0009] Further, the molar ratio of octamethylcyclotetrasiloxane, tetramethyldisiloxane, and tetramethylammonium hydroxide described in step A1 is 2.4:1:2.

[0010] Further, the molar ratio of 4-aminobenzimidazole, triethylamine, and acryloyl chloride described in step A2 is 1:1.1:1, the molar ratio of the modifier to dihydropolysiloxane is 2:1, and the dosage of chloroplatinic acid is 1‰ of the mass of the modifier.

[0011] Further, the modified abrasive is prepared by the following steps:

[0012] Step B1: Mix aluminum chloride hexahydrate, 1,2,4,5-benzenetetracarboxylic acid, 2-aminoterephthalic acid, and N,N-dimethylformamide evenly, and react at a temperature of 110 - 115°C for 20 - 24 hours to obtain an aluminum-based organic framework.

[0013] Step B2: Mix the aluminum-based organic framework, 3-isocyanatopropyltrimethoxysilane, and DMF, introduce nitrogen protection, and react at a rotation speed of 200 - 300 r / min and a temperature of 25 - 30°C for 3 - 5 hours to obtain a modified aluminum-based organic framework.

[0014] Step B3: Mix the modified aluminum-based organic framework, tetraethyl orthosilicate, methyltriethoxysilane, dimethyldiethoxysilane, and absolute ethanol evenly, stir and add deionized water and hydrochloric acid at a rotation speed of 200 - 300 r / min and a temperature of 65 - 70°C, react for 2 - 3 hours, then raise the temperature to 120 - 130°C and continue to react for 1 - 1.5 hours to obtain a precursor.

[0015] Step B4: Place the precursor in a tube furnace, raise the temperature to 600 - 650°C at a heating rate of 2 - 5°C / min, hold for 2 - 3 hours, then raise the temperature to 800 - 850°C, hold for 1 - 1.5 hours, raise the temperature to 900 - 1000°C, and hold for 1 - 1.5 hours under a nitrogen atmosphere to obtain the modified abrasive.

[0016] Further, the dosage ratio of aluminum chloride hexahydrate, 1,2,4,5-benzenetetracarboxylic acid, 2-aminoterephthalic acid, and N,N-dimethylformamide described in step B1 is 5 mmol:12 mmol:1.8 mmol:60 mL.

[0017] Further, the molar ratio of the amino group on the aluminum-based organic framework to 3-isocyanatopropyltrimethoxysilane described in step B2 is 1:1.

[0018] Further, the dosage ratio of the modified aluminum-based organic framework, tetraethyl orthosilicate, methyltriethoxysilane, dimethyldiethoxysilane, absolute ethanol, deionized water, and hydrochloric acid described in step B3 is 1 g: 5 mmol: 2 mmol: 1 mmol: 20 mL: 5 mL: 1 mL.

[0019] Beneficial effects of the present invention: A polishing liquid for a chip disclosed by the present invention comprises the following raw materials: a modified abrasive, hydrogen peroxide, glycine, a modified inhibitor, polyethylene glycol, and water. The pH value is adjusted to 8.5 with potassium hydroxide to obtain the polishing liquid. The modified inhibitor is prepared by ring-opening polymerization of octamethylcyclotetrasiloxane as a raw material and then end-capping with tetramethyldisiloxane to obtain dihydrogen polysiloxane. 4-Aminobenzotriazole and acryloyl chloride are reacted so that the amino group on 4-aminobenzotriazole reacts with the acyl chloride group on acryloyl chloride to obtain a modifier. The modifier and dihydrogen polysiloxane are reacted so that the double bond on the modifier reacts with the Si-H bond on dihydrogen polysiloxane to obtain the modified inhibitor.

[0020] The modified abrasive is prepared by reacting aluminum chloride hexahydrate, 1,2,4,5-benzenetetracarboxylic acid, and 2-aminoterephthalic acid as raw materials to obtain an aluminum-based organic framework. The aluminum-based organic framework and 3-isocyanatopropyltrimethoxysilane are reacted so that the amino group on the aluminum-based organic framework reacts with the isocyanate group on 3-isocyanatopropyltrimethoxysilane to obtain a modified aluminum-based organic framework. The modified aluminum-based organic framework, tetraethyl orthosilicate, methyltriethoxysilane, and dimethylethoxysilane are hydrolyzed and polycondensed to form a composite structure of polysiloxane and the modified aluminum-based organic framework to obtain a precursor. The precursor is kept at a high temperature to form an alumina composite silica structure to obtain the modified abrasive.

[0021] The addition of the modified inhibitor can form a dense passivation film on the copper surface, effectively preventing the corrosion of the copper surface by the polishing liquid. The modified filler has silica as the main material and alumina embedded on the surface and inside, making the modified filler not easy to agglomerate while having high hardness, reducing the viscosity of the polishing liquid, and thus making the polishing liquid easier to clean, reducing the process, and improving the polishing efficiency. Specific embodiments

[0022] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0023] Example 1, a preparation method of a polishing liquid for a chip, specifically comprises the following steps:

[0024] Step A1: Octamethylcyclotetrasiloxane, tetramethyldisiloxane, tetramethylammonium hydroxide and dimethyl sulfoxide are mixed, and nitrogen is introduced for protection. The reaction is carried out for 10 h at a rotation speed of 120 r / min and a temperature of 90 °C to obtain dihydrogen polysiloxane;

[0025] Step A2: 4-aminobenzotriazole, triethylamine and chloroform are mixed, stirred and acryloyl chloride is added at a rotation speed of 150 r / min and a temperature of 0 °C, and the reaction is carried out for 2 h to obtain a modifier. The modifier, dihydrogen polysiloxane, chloroplatinic acid and N,N-dimethylformamide are mixed evenly, and the reaction is carried out for 5 h at a rotation speed of 120 r / min and a temperature of 70 °C to obtain a modified inhibitor;

[0026] Step A3: Weigh the following percentage of raw materials: 0.5% of modified abrasive, 1% of hydrogen peroxide, 2% of glycine, 0.1% of modified inhibitor and 0.5% of polyethylene glycol, and the balance is water. The raw materials are mixed evenly, and potassium hydroxide is added to adjust the pH value to 8.5 to obtain a polishing liquid for chips.

[0027] The molar ratio of octamethylcyclotetrasiloxane, tetramethyldisiloxane and tetramethylammonium hydroxide described in Step A1 is 2.4:1:2.

[0028] The molar ratio of 4-aminobenzimidazole, triethylamine and acryloyl chloride described in Step A2 is 1:1.1:1, the molar ratio of the modifier and dihydrogen polysiloxane is 2:1, and the dosage of chloroplatinic acid is 1‰ of the mass of the modifier.

[0029] The average molecular weight of the polyethylene glycol described in Step A3 is 2000.

[0030] The described modified abrasive is prepared by the following steps:

[0031] Step B1: Aluminum chloride hexahydrate, 1,2,4,5-benzenetetracarboxylic acid, 2-aminoterephthalic acid and N,N-dimethylformamide are mixed evenly, and the reaction is carried out for 20 h at a temperature of 110 °C to obtain an aluminum-based organic framework;

[0032] Step B2: The aluminum-based organic framework, 3-isocyanatopropyltrimethoxysilane and DMF are mixed, nitrogen is introduced for protection, and the reaction is carried out for 3 h at a rotation speed of 200 r / min and a temperature of 25 °C to obtain a modified aluminum-based organic framework;

[0033] Step B3: The modified aluminum-based organic framework, tetraethyl orthosilicate, methyltriethoxysilane, dimethyldiethoxysilane and absolute ethanol are mixed evenly, stirred at a rotation speed of 200 r / min and a temperature of 65 °C, and deionized water and hydrochloric acid are added, and the reaction is carried out for 2 h and then heated to 120 °C and the reaction is continued for 1 h to obtain a precursor;

[0034] Step B4: Place the precursor in a tube furnace. Under the condition of a heating rate of 2 °C / min, heat it to 600 °C, keep it for 2 h, then heat it to 800 °C, keep it for 1 h, and then heat it to 900 °C. Under a nitrogen atmosphere, keep it for 1 - 1.5 h to obtain the modified abrasive.

[0035] The dosage ratio of aluminum chloride hexahydrate, 1,2,4,5 - benzenetetracarboxylic acid, 2 - aminoterephthalic acid, and N,N - dimethylformamide described in Step B1 is 5 mmol:12 mmol:1.8 mmol:60 mL.

[0036] The molar ratio of the amino group on the aluminum - based organic framework described in Step B2 to 3 - isocyanatopropyltrimethoxysilane is 1:1.

[0037] The dosage ratio of the modified aluminum - based organic framework, tetraethyl orthosilicate, methyltriethoxysilane, dimethyldiethoxysilane, absolute ethanol, deionized water, and hydrochloric acid described in Step B3 is 1 g:5 mmol:2 mmol:1 mmol:20 mL:5 mL:1 mL.

[0038] Example 2, A preparation method of a polishing liquid for a chip, specifically including the following steps:

[0039] Step A1: Mix octamethylcyclotetrasiloxane, tetramethyldisiloxane, tetramethylammonium hydroxide, and dimethyl sulfoxide, introduce nitrogen protection, and react for 10 h under the conditions of a rotation speed of 120 r / min and a temperature of 95 °C to obtain dihydro - polysiloxane;

[0040] Step A2: Mix 4 - aminobenzotriazole, triethylamine, and chloroform, stir and add acryloyl chloride under the conditions of a rotation speed of 150 r / min and a temperature of 0 °C, and react for 3 h to obtain a modifier. Mix the modifier, dihydro - polysiloxane, chloroplatinic acid, and N,N - dimethylformamide evenly, and react for 5 h under the conditions of a rotation speed of 120 r / min and a temperature of 75 °C to obtain a modified inhibitor;

[0041] Step A3: Weigh the following percentage of raw materials: 0.6% of modified abrasive, 1.1% of hydrogen peroxide, 2.3% of glycine, 0.3% of modified inhibitor, and 0.8% of polyethylene glycol, with the balance being water. Mix the raw materials evenly, and add potassium hydroxide to adjust the pH value to 8.5 to obtain the polishing liquid for the chip.

[0042] The molar ratio of octamethylcyclotetrasiloxane, tetramethyldisiloxane, and tetramethylammonium hydroxide described in Step A1 is 2.4:1:2.

[0043] The molar ratio of 4-aminobenzimidazole, triethylamine and acryloyl chloride described in step A2 is 1:1.1:1, the molar ratio of the modifier and dihydropolysiloxane is 2:1, and the dosage of chloroplatinic acid is 1‰ of the mass of the modifier.

[0044] The average molecular weight of the polyethylene glycol described in step A3 is 2000.

[0045] The modified abrasive is prepared by the following steps:

[0046] Step B1: Mix aluminum chloride hexahydrate, 1,2,4,5-benzenetetracarboxylic acid, 2-aminoterephthalic acid and N,N-dimethylformamide evenly, and react at a temperature of 110 °C for 22 h to obtain an aluminum-based organic framework.

[0047] Step B2: Mix the aluminum-based organic framework, 3-isocyanatopropyltrimethoxysilane and DMF, introduce nitrogen protection, and react at a rotation speed of 200 r / min and a temperature of 30 °C for 4 h to obtain a modified aluminum-based organic framework.

[0048] Step B3: Mix the modified aluminum-based organic framework, tetraethyl orthosilicate, methyltriethoxysilane, dimethyldiethoxysilane and absolute ethanol evenly, stir and add deionized water and hydrochloric acid at a rotation speed of 200 r / min and a temperature of 70 °C, react for 2 h, then raise the temperature to 125 °C and continue to react for 1.3 h to obtain a precursor.

[0049] Step B4: Place the precursor in a tubular furnace, heat it to 630 °C at a heating rate of 2 °C / min, hold for 3 h, then heat it to 830 °C, hold for 1.5 h, heat it to 9950 °C, and hold for 1 h under a nitrogen atmosphere to obtain the modified abrasive.

[0050] The dosage ratio of aluminum chloride hexahydrate, 1,2,4,5-benzenetetracarboxylic acid, 2-aminoterephthalic acid and N,N-dimethylformamide described in step B1 is 5 mmol:12 mmol:1.8 mmol:60 mL.

[0051] The molar ratio of the amino group on the aluminum-based organic framework and 3-isocyanatopropyltrimethoxysilane described in step B2 is 1:1.

[0052] The dosage ratio of the modified aluminum-based organic framework, tetraethyl orthosilicate, methyltriethoxysilane, dimethyldiethoxysilane, absolute ethanol, deionized water and hydrochloric acid described in step B3 is 1 g:5 mmol:2 mmol:1 mmol:20 mL:5 mL:1 mL.

[0053] Example 3, a preparation method of a polishing liquid for a chip, specifically includes the following steps:

[0054] Step A1: Mix octamethylcyclotetrasiloxane, tetramethyldisiloxane, tetramethylammonium hydroxide and dimethyl sulfoxide, introduce nitrogen for protection, and react for 12 h under the conditions of a rotation speed of 150 r / min and a temperature of 95 °C to obtain dihydro polysiloxane;

[0055] Step A2: Mix 4-aminobenzotriazole, triethylamine and chloroform, stir and add acryloyl chloride under the conditions of a rotation speed of 200 r / min and a temperature of 0 °C, and react for 3 h to obtain a modifier. Mix the modifier, dihydro polysiloxane, chloroplatinic acid and N,N-dimethylformamide evenly, and react for 6 h under the conditions of a rotation speed of 150 r / min and a temperature of 80 °C to obtain a modified inhibitor;

[0056] Step A3: Weigh the following percentage of raw materials: 0.8% of modified abrasive, 1.2% of hydrogen peroxide, 2.5% of glycine, 0.5% of modified inhibitor and 1% of polyethylene glycol, and the balance is water. Mix the raw materials evenly, add potassium hydroxide to adjust the pH value to 8.5 to obtain a polishing liquid for chips.

[0057] The molar ratio of octamethylcyclotetrasiloxane, tetramethyldisiloxane and tetramethylammonium hydroxide described in Step A1 is 2.4:1:2.

[0058] The molar ratio of 4-aminobenzimidazole, triethylamine and acryloyl chloride described in Step A2 is 1:1.1:1, the molar ratio of the modifier to dihydro polysiloxane is 2:1, and the dosage of chloroplatinic acid is 1‰ of the mass of the modifier.

[0059] The average molecular weight of the polyethylene glycol described in Step A3 is 2000.

[0060] The described modified abrasive is prepared by the following steps:

[0061] Step B1: Mix aluminum chloride hexahydrate, 1,2,4,5-benzenetetracarboxylic acid, 2-aminoterephthalic acid and N,N-dimethylformamide evenly, and react for 24 h under the condition of a temperature of 115 °C to obtain an aluminum-based organic framework;

[0062] Step B2: Mix the aluminum-based organic framework, 3-isocyanatopropyltrimethoxysilane and DMF, introduce nitrogen for protection, and react for 5 h under the conditions of a rotation speed of 300 r / min and a temperature of 30 °C to obtain a modified aluminum-based organic framework;

[0063] Step B3: Mix the modified aluminum-based organic framework, tetraethyl orthosilicate, methyltriethoxysilane, dimethyldiethoxysilane, and absolute ethanol evenly. Under the conditions of a rotation speed of 300 r / min and a temperature of 70 °C, stir and add deionized water and hydrochloric acid, and react for 3 h. Then, raise the temperature to 130 °C and continue to react for 1.5 h to obtain a precursor.

[0064] Step B4: Place the precursor in a tube furnace. Under the condition of a heating rate of 5 °C / min, raise the temperature to 650 °C, hold for 3 h, then raise the temperature to 850 °C, hold for 1.5 h, and then raise the temperature to 1000 °C. Under a nitrogen atmosphere, hold for 1.5 h to obtain the modified abrasive.

[0065] The dosage ratio of aluminum chloride hexahydrate, 1,2,4,5-benzenetetracarboxylic acid, 2-aminoterephthalic acid, and N,N-dimethylformamide described in Step B1 is 5 mmol: 12 mmol: 1.8 mmol: 60 mL.

[0066] The molar ratio of the amino group on the aluminum-based organic framework described in Step B2 to 3-isocyanatopropyltrimethoxysilane is 1:1.

[0067] The dosage ratio of the modified aluminum-based organic framework, tetraethyl orthosilicate, methyltriethoxysilane, dimethyldiethoxysilane, absolute ethanol, deionized water, and hydrochloric acid described in Step B3 is 1 g: 5 mmol: 2 mmol: 1 mmol: 20 mL: 5 mL: 1 mL.

[0068] Comparative Example 1: In this comparative example, benzotriazole is used instead of the modified inhibitor compared with Example 1, and the remaining steps are the same.

[0069] Comparative Example 2: In this comparative example, alumina is used instead of the modified abrasive compared with Example 1, and the remaining steps are the same.

[0070] Comparative Example 3: In this comparative example, silica is used instead of the modified abrasive compared with Example 1, and the remaining steps are the same.

[0071] Polish and process the polishing fluids prepared in Examples 1-3 and Comparative Examples 1-3 under the conditions of a pressure of 1 psi, a polishing disc rotation speed of 70 r / min, a polishing head rotation speed of r / min, a polishing fluid flow rate of 100 mL / min, and a polishing time of 5 min, measure the surface roughness, and use deionized water for the polished sample. Under the condition of a frequency of 40 kHz, perform ultrasonic treatment for 10 min to observe whether there is residue on the surface. The detection results are shown in Table 1 below.

[0072] Table 1

[0073]

[0074] As can be seen from Table 1, the present application has good polishing efficiency and is easy to clean.

[0075] The above content is only an example and illustration of the concept of the present invention. Those skilled in the art of this technology can make various modifications or supplements to the described specific embodiments or use similar ways to replace them. As long as they do not deviate from the concept of the invention or exceed the scope defined by this claim book, they should all belong to the protection scope of the present invention.

Claims

1. A method for preparing a chip polishing liquid, characterized in that: The specific steps include: Step A1: octamethylcyclotetrasiloxane, tetramethyldisiloxane, tetramethylammonium hydroxide and dimethyl sulfoxide are mixed, nitrogen is introduced for protection, and the mixture is reacted to obtain dihydrogenpolysiloxane; Step A2: 4-aminobenzotriazole, triethylamine and chloroform are mixed and stirred, and acryloyl chloride is added to react to obtain a modifier, and the modifier, dihydrogenpolysiloxane, chloroplatinic acid and N,N-dimethylformamide are mixed and reacted to obtain a modified inhibitor; Step A3: Weigh the following percentages of raw materials: 0.5-0.8% of modified abrasive, 1-1.2% of hydrogen peroxide, 2-2.5% of glycine, 0.1-0.5% of modified inhibitor and 0.5-1% of polyethylene glycol, with the remainder being water, mix the raw materials evenly, add potassium hydroxide to adjust the pH value to 8.5, and prepare a chip polishing solution.

2. The method for preparing a chip polishing liquid according to claim 1, characterized in that: The molar ratio of octamethylcyclotetrasiloxane, tetramethyldisiloxane and tetramethylammonium hydroxide described in step A1 is 2.4:1:

2.

3. The method for preparing a chip polishing liquid according to claim 1, characterized in that: The molar ratio of 4-aminobenzimidazole, triethylamine and acryloyl chloride in step A2 is 1:1.1:1, and the molar ratio of the modifier and dihydrogenpolysiloxane is 2:

1.

4. The method for preparing a chip polishing liquid according to claim 1, characterized in that: The modified abrasive is prepared by the following steps: Step B1: aluminum chloride hexahydrate, 1,2,4,5-benzenetetracarboxylic acid, 2-aminoterephthalic acid and N,N-dimethylformamide are mixed and reacted to prepare an aluminum-based organic framework; Step B2: mixing an aluminum-based organic framework, 3-isocyanatepropyltrimethoxysilane and DMF, introducing nitrogen gas for protection, and reacting to obtain a modified aluminum-based organic framework; Step B3: mixing and stirring the modified aluminum-based organic framework, tetraethyl orthosilicate, methyltriethoxysilane, dimethyldiethoxysilane and anhydrous ethanol, and adding deionized water and hydrochloric acid to react to obtain a precursor; Step B4: placing the precursor in a tube furnace, heating and maintaining the temperature under a nitrogen atmosphere to obtain a modified abrasive.

5. The method for preparing a chip polishing liquid according to claim 4, characterized in that: The amount ratio of aluminum chloride hexahydrate, 1,2,4,5-benzenetetracarboxylic acid, 2-aminoterephthalic acid and N,N-dimethylformamide described in step B1 is 5mmol:12mmol:1.8mmol:60mL.

6. The method for preparing a chip polishing liquid according to claim 4, characterized in that: The molar ratio of amino group and 3-isocyanatepropyltrimethoxysilane on the aluminum-based organic framework described in step B2 is 1:

1.

7. The method for preparing a chip polishing liquid according to claim 4, characterized in that: The amount ratio of the modified aluminum-based organic framework, tetraethyl orthosilicate, methyltriethoxysilane, dimethyldiethoxysilane, anhydrous ethanol, deionized water and hydrochloric acid described in step B3 is 1g:5mmol:2mmol:1mmol:20mL:5mL:1mL.

8. A chip polishing liquid, characterized in that: Prepared according to any one of claims 1 to 7.

Images