DD299520A5 - PROCESS FOR THE PRODUCTION OF POROUS LAYERS WITH FITNESS AS A SUPPORTING LAYER FOR POLISHING AGENTS - Google Patents

Abstract

The invention relates to a method for producing porous layers with different Porositaet, which are suitable as a carrier layer for polishing agents. The system is used to process semiconductor materials. Textile carrier materials made of synthetic fibers are coated with a polymer mixture in solution and solidification of the layer by coagulation with the addition of non-solvent, which mixes with the solvent, achieved. It depends on the use of polymers with different Strukturbildungsvermoeegen in the coagulation of solution. {Polishing; Semiconductor materials; aids; Laminate; polyurethane; polyvinyl chloride; Solution; coagulation; Structure of the surface; Porosity; microporosity}

Description

Tensile strength (N / mm ² ) 43 to 65

Hydrolysis stability (%) (residual tensile strength) 90 to 100

Young's modulus (N / mm ² ) at 100% elongation 7 to 30

Elongation (%) 300 to 600

5. The method according to claim 3, characterized in that the polyvinyl chloride has a K value in the limits of 66 to 71.

Field of application of the invention

The invention relates to a method for producing porous layers which have a suitability as a carrier of polishing agent. These layers are produced on textile substrates and contribute to the chemical-mechanical polishing process of silicon wafers. This proportion is characterized by the speed of the polishing process.

Characteristic of the known state of the art

Microporous polishing cloth as a carrier of polishing agent is mentioned in terms of some structural features (Fa, Geos, U.S.A., Summary of recent developments in polishing, 1982). In this document, the achievable polishing effect depending on the polishing agent, the temperature and the pressure is described. The influence of the carrier material on the polishing effect is called unexplainable (magic).

Notes on the preparation of the polishing cloth are not specified. Of 18 patents that cover the basics of manufacturing microporous material, only one gives an indication of eligibility as a polishing cloth. This is US 3,067,482, a process patent for the production of soft synthetic suede.

Briefly, this process consists in preparing a nonwoven web of staple fibers, impregnating it with a solution of a polymer in an organic liquid which is a non-solvent for the fibers, and the liquid organic solvent from the impregnated web with an inert liquid which is a non-solvent for the impregnating agent and the fibers and is miscible with the liquid organic solvent for the impregnating agent, so that the impregnating agent is converted into a matrix for the nonwoven fabric, which has virtually no adhesiveness to the fibers. After complete extraction of the organic solvent from the impregnated nonwoven, the inert liquid is removed by evaporation. The impregnant which forms the non-adherent matrix for the nonwoven fabric is a low modulus polymer, i. h "it has a tensile stress at 5% elongation of at least 0.35kp / cm ² and preferably less than 3.5kp / cm ²

 The material produced by this technology showed in trial only a small suitability as a polish carrier.

Object of the invention

The object of the invention is to produce a material which can receive the polishing agent used for the chemical-mechanical polishing of semiconductor materials, can be used in the usual production facilities for this process and produces good polishing results.

The essence of the invention

The object of the invention is to develop a process which, when the coagulation principle is applied to a solution of two special polymers, leads to the formation of layers having a characteristic surface structure which are suitable for the chemical-mechanical polishing process in terms of their chemical-physical properties.

It has been rumored that the production of porous layers suitable as a backing for polishing agents, for the processing of Semiconductor materials, by coating textile substrates made of synthetic fibers with the solution of a Polymer mixture and solidification of this layer by coagulation with non-solvent for the polymers, wherein Non-solvent and solvent mix, then takes place when the polymers used in the coagulation

have different structure-forming ability, which must be tailored to the requirement of suitability as a carrier layer for polishing agents for processing semiconductor materials.

Suitable is the use of a polyetherurethane, according to WP C 08 G / 2972058 or according to Example 1 of this invention,

which coagulates microporously but forms an unstable layer which collapses upon further processing, d. h., the

Microporosity loses and also with respect to the layer thickness subsequently when moving over pulleys Loss of uniformity, which is why this polyether urethane in terms of a second polymer component in the solution

the structure must be solidified.

Solidifier and thus stabilizer for microporosity is polyvinyl chloride, which prevents the polyurethane layer at

the solidification processes, washing and drying, collapsing to a transparent layer.

However, the microporosity is formed solely by the polyurethane. The polyvinyl chloride in turn forms macropores that are briefly under

begin the layer surface and extend in an elongated form in the interior of the layer, usually in the form of

Hair follicles, but also pear-shaped. Their axial ratio is / 1: 2.5 to 1: 3.5. The sidewalls of these macropores

are microporous. The thin surface layer is split or abraded. After that, the most well educated

Outlet channel open. Suitable polyether urethane shows a Ε-module in the limits of 7 N / mm ² to 30NVmm ² . Daraj's made transparent Film has tensile strength values between 43 N / mm ² and 65 N / mm ² and a hydrolysis resistance of at least 90%,

measured by tensile strength after 14 days of tropic test.

Suitability as polyvinyl chloride have both emulsion and suspension polymers. The K value of these products is

appropriate between 66 and 71.

Of the total polymer use, the polyvinyl chloride content is within the limits of 10% to 30%. It was found that with

increasing polyvinyl chloride content increases the number of elongated macropores. However, the hardness of the coagulating layer also increases, and this is advantageous only in a limited range, while higher rigidity is detrimental. If the material is too stiff, then the Stoffa 'exchange during the polishing process between the polish supply in the macropores and the polishing agent layer on the support is insufficient. In such case, the removal per unit time decreases faster.

The coagulation process of the polymers in solution takes place in the dimethylformamide / water system. Also Tetrahydrofuran kit is suitable for structuring the polymers in the layer together with water. The textile carrier material coated with the polymer solution is expediently introduced into the coagulation process Water bath containing 5% to 35% of dimethylformamide. Is the content of dimethylformamide in the coagulation bath too

low, creates a layer for practical coagulation virtually impermeable layer and the coagulation is incomplete. If the content of dimethylformamide in the coagulation bath is too high, the formation of microporon is disturbed. In both

Falling macropores form in different, undesirable arrangement. To prepare the polymer mixture in solution, one starts from a 25% strength polyurethane solution and sets a 10% strength Polyvinyl chloride solution too. It can be seen that with increasing polyvinyl chloride use, this solution dilutes. With

As the dilution increases, the viscosity of the coating solution decreases. This reduces the application quantities and thus the layer thicknesses and, after coagulation, the pore depth of the macropores is too low if the dilution is too great. In addition, in this case, the pore density is not sufficient.

The solution is sensitized before coating. For this purpose, it receives an addition of precipitant in the range 2 = 7% based on

the polyurethane solids content.

The coagulation conditions together with the coating formulation are the prerequisite for the appropriate Structure formation. The existing structure influences the removal rate.

Example 1 ' ,

100 g of a polytetramethylene ether glycol having an average molar mass of 1500 are reacted in 134 g of dimethylformamide with 33.3 g of 4,4'-diphenylmethane diisocyanate for 90 minutes at 50 ° C. to give a prepolymer same amount of dimethylformamide. This reaction mixture is 60 kept at 50 ° C min and then has an OH number from 71 to. The pre-extended prepolymer is then reacted with 62.5 g of 4,4'-diphenylmethane diisocyanate additional 60min at 5O ⁰ C and 62 5g dimethylformamide added.

The preadduct solution diluted with 431 g of dimethylformamide is slowly added to 2.5 ml of hydrazine hydrate (1 ml of hydrazine hydrate

contains 531 mg of hydrazine) in 2.5 ml of dimethylformamide metered until the dynamic viscosity has reached values between 15000 mPa · s and 2000OmPa · s.

In this formulation, a dynamic viscosity of 1990OmPa · s was determined. The polyether urethane shows the following properties as a transparent film:

Tensile strength (N / mm ² ) 56.3

Elastic modulus at 100% elongation (N / mm ² ) 13.9

- Hydrolysis stability (residual tensile strength) (%) 97

- Elongation (%) 490

61.6 parts by weight of 25% solution of the polyether polyurethane prepared above in dimethylformamide and 60 parts by weight of a 10% solution of polyvinyl chloride (PVC-E 6921 M 20, VEB Chemische Werke Buna) in dimethylformamide are mixed with stirring. Sensitization is carried out by stirring in 0.6 parts by weight of acramine black FBB (Bayer AG), about half of which is water, ie precipitant. The solution is deaerated for 1 hour at a vacuum of 2.5 kPa with simultaneous stirring. The solution prepared in this way has used a viscosity of 1600 mPa · s (at 25 ⁰ C) and for the coating of 0,8-0,9mm thick needle felt with a fiber composition of 60% Polyoster- and 40% polypropylene fibers. On a suitable for the application of the coagulation process coating system, the fleece of the settlement

fed to a squeegee, with which the solution is applied at a blade gap setting of 1.8 mm. The coated one

Needle fleece is then passed through a bath containing dimethylformamide-water mixture in the ratio 30:70 and

whose temperature is set to 25 ⁰ C. The transport speed of the web is dependent on the

Bath dimensions chosen so that the material remains β minutes in the bath and the coated side after 3 minutes for the first time

comes in contact with a roller.

After the layer is sufficiently solidified in the coagulation bath, the material is placed in a washing section with water

washed out to remove the solvent dimethylformamide to a level of <0.5%. After washing, the material is dried at 110.degree. The pores of the porous polyurethane layer are opened by a surface grinder on a roll grinder with grit size 240 grit paper.

With this material, polishing of silicon wafers using silica sol 30K at pH 11.5 became a Removal rate of 1.31 pm / min achieved. Example 2

100 g of a mixture of the dehydrated polyether diols polyoxypropylene glycol and polyoxyethylene glycol having an average molar mass of the mixture of 730 are reacted in 169 g dimethylformamide with 68.8 g of 4,4'-diphenylmethane diisocyanate for 120 minutes at BO ⁰ C to give a prepolymer.

In the second step, the extension of the prepolymer by addition of 37.1 g of 1,4-butanediol in the same amount Dimethylformamide. The reaction mixture is kept 60 min at 5O ⁰ C and daqach has an OH number of 150. The pre-extended prepolymer is in the 3rd step mit85,9g4,4'-Dlphenylmethandiisocyanatweitere60min at 5O ⁰ C

implemented and added 85.9g DMF.

The preadduct solution diluted with 586 g of dimethylformamide is slowly added to 4 ml of hydrazine hydrate (1 ml of hydrazine hydrate

531 mg of hydrazine) in 4 ml of dimethylformamide until the dynamic viscosity has reached values between 1500OmPa.s and 2000OmPa.s. With this recipe, a dynamic viscosity of 1680OmPa s was found.

Properties of the transparent film are: Tensile strength (N / mm ² ) 45.1 Young's modulus at 100% elongation (N / mm ² ) 20.3

Elongation (%) 340

100 parts by weight of this solution and 5 parts by weight of PVC-E 6642 M10 (VEB Chemical plants Buna) are under intense

Stir mixed. The mixture of the polymer solutions are 25.5 parts by weight of dimethylformamide and 0.5 parts by weight Acramin black FBB (Bayer AG) added. The solution is deaerated for 90 minutes at a vacuum of 2.5 kPa with simultaneous stirring at 200 rpm. The solution prepared in this way has a viscosity of 1270OmPa.s at 25 ⁰ C. Coating and the further process route are carried out analogously to Example 1. The material yielded a polish at pH 11.5 when polishing silicon wafers using silica sol 30K as the polishing agent Removal rate of 1.24 mm / min.

Claims (4)

1. A process for producing porous layers with different porosity, suitable as a carrier layer for polishing agents for processing semiconductor materials by coating textile substrates made of synthetic fibers with a polymer mixture in solution and solidification of the layer by coagulation with non-solvent for the polymers, but which is miscible with the solvent characterized by the use of polymers having different structure-forming capacity in coagulation from solution. 2. The method according to claim 1, characterized by using polyurethane, which forms a microporous non-stable layer during the coagulation process. 3. The method according to claim 1, characterized by using polyvinyl chloride as a solidifier and builder of macropores. 4. The method according to claim 2, characterized in that the polyurethane as a transparent film has the following properties in the following limits