FR2870344A1 - Polishing solution composition measuring and/or controlling method, e.g. for polishing silicon wafer, involves determining possible change of composition of solution during solution distribution process - Google Patents

Abstract

Polishing solution composition measuring and/or controlling method involves measuring absorption spectrum of electromagnetic radiation transmitted across and/or reflected by a part of a polishing solution. Composition of the solution is determined using a spectroscopic analysis in the near infra red field or in the absorption spectrum. Possible change of the composition is determined during the polishing solution distribution process. An independent claim is also included for a system for measuring and/or controlling composition of polishing solution distributed by a polishing solution distribution system.

Description

Method and system for controlling the solution composition by

near infrared spectroscopy

  The present invention relates to a method for measuring and / or controlling the composition of at least one polishing solution dispensed by at least one polishing solution delivery system for polishing semiconductor wafers or other circuits using nanotechnologies and well known especially under the name of type MEMS. It also relates to a system for implementing such a method.

  The purpose of such a process is to analyze continuously, in real time, the complex mixture composition of the polishing solution type, in order to know the concentration of the various constituents present in the mixture or mixtures. This is to ensure the physicochemical properties necessary for the use of said mixtures and in particular the polishing of the surface of silicon wafers or other MEMS-type wafers. Throughout the remainder of the description, the term "polishing solution" refers to any mixture (solution or emulsion) of one or more liquids (water, etc.) with one or more additives in solid form (abrasive particles, etc.). ..) or liquid (hydrogen peroxide, surfactants, etc ...) whose composition can be measured and / or controlled in the same way as that of polishing solutions, regardless of their composition and use.

  The methods and systems of the type described above make it possible to predict and prevent production incidents by obtaining better control of the composition of mixtures meeting the specifications of the production of a range of semiconductors (or MEMS) and avoid for example that these mixtures are considered unusable while they still meet the standards of use provided in the roadmap of their manufacture.

  Currently, analytical methods for characterizing the overall composition of polishing solutions, for example, can not be performed online on the distribution system. Samples taken are transported to a laboratory for further analysis by ion chromatography or HPLC (High Performance Liquid Chromatography) techniques. The disadvantage of these methods lies in the cumbersome implementation and the long time required to obtain a quantification of the product which can cause a delay in the detection of incidents on the formulation of the mixture, since such an analysis can not be carried out in any way. case be carried out continuously. The delay in incident detection on the formulation of the mixture may result in a degradation of the so-called CMP (chemical mechanical polishing) polishing quality of the wafer surface.

  In addition, the preparation of the samples can lead to transformations of the chemical nature of the constituents of the solution and can inevitably lead to an increase in the measurement uncertainty.

  Quantification of the constituents of the mixture by conventional HPLC or ion chromatography techniques further requires the identification of the constituents in order to plot calibration curves for each constituent. The identification of the constituents can be achieved through the use of specific detectors. This step makes the whole analysis longer and heavier to implement.

  The known technique of visible ultraviolet spectroscopy can allow measurement in line, in principle. However, such a technique has a low sensitivity of the measurement, because of the low absorbance of the solutions which must be pre-diluted before analysis. The diffraction phenomena of the particles (for example of abrasives) that may be present in the mixtures make it even more difficult to analyze by ultraviolet radiation in the visible.

  The measurement of the refractive index of the solutions making it possible to deduce a variation in the concentration of several constituents of a mixture has also already been considered in the literature. This method applies only in the case of binary mixture only, it has the disadvantage of being highly dependent on the temperature of the solution.

  Furthermore, it is known from WO03 / 057947 a method and system for spectroscopic analysis in the near-infrared Fourier transform, but intended only to measure variations in copper concentration or acidity of a solution based on copper salt for electrochemically depositing copper on a surface of a circuit.

  At present, therefore, there is no simple, reliable and precise method of measurement and / or control which can, if necessary, make it possible, on-line measurement of the overall composition of a polishing solution flowing in a cooling circuit. solution distribution.

  The method according to the invention and the system for implementing this method make it possible to respond to the problem posed.

  For this purpose, the method according to the invention is characterized in that it comprises the following steps: a) directing the electromagnetic radiation emitted by a source in the near-infrared range corresponding to a range of wavelengths between 800 and 2100.10-9 m on at least a part of the at least one polishing solution, b) measuring the absorption spectrum of this electromagnetic radiation transmitted through and / or reflected by said part of the at least one solution polishing, c) determining the composition of said portion of the at least one polishing solution by spectroscopic analysis in the near-infrared range on the radiation absorption spectrum by said solution, d) If necessary, repeat steps a) to c) above, e) any changes in the composition of the polishing solution during the polishing solution distribution process are determined.

  Preferably, a light guiding device having at least one optical fiber will be used to conduct the electromagnetic radiation from its source substantially to the polishing solution.

  The point of use of the polishing solution will generally be located at a certain distance from the place where said source of electromagnetic radiation is located (rarely next to it, which makes the use of optical fibers to conduct the radiation very interesting). The polishing solution composition of a plurality of polishing solution delivery networks or systems can be measured and / or monitored simultaneously and / or sequentially. It is also possible according to the invention to measure and / or continuously monitor the composition of the polishing solution.

  Optionally, it is also possible to extract a sample of the polishing solution to transfer it to the place where it will be subjected to steps a) to c) optionally d). But this is not the preferred mode of use of the invention, the preferred embodiment of the invention being a measurement and / or continuous control of the composition of at least one polishing solution in at least one a polishing solution dispensing system.

  According to a variant of the invention, at least one polishing solution distribution network or system comprises a continuous distribution loop of the polishing solution from a dispensing drum until the solution is returned to said dispensing barrel. loop having at least one point of use of said solution. (A system of this type is described in patent EP 0980 741 belonging to the Applicant). In this type of dispensing system, a continuous circulation of the polishing solution from the dispensing drum is preferably carried out until the return to the dispensing drum, so as to avoid the problems (well known per se) of the drying of the dispensing system. solution and thus creating agglomerates that can be destructive layers of the circuits they are supposed to polish.

  The polishing solution is preferably prepared in situ by mixing additives with a base solution (deionized water and / or other liquid), the polishing solution part of process step b) being a part of the process. polishing solution available after preparation.

  Preferably, the preparation of the polishing solution is carried out by mixing the additives in a mixing drum with the base solution and by circulating said solution thus prepared in a preparation loop in order to homogenize it and to avoid problems. drying, formation of agglomerates, etc ..., until this solution is partially transferred into the distribution loop, the solution part of step b) of the process being part of the preparation loop.

  According to another variant of the invention, an inert gas is used to push the polishing solution and circulate it. The inert gas will be a gas such as nitrogen, argon, helium, krypton, xenon, etc ... this inert gas being of electronic purity that is to say having the degree of purity ( particles, impurities, etc.) required for the manufacture of the semiconductors concerned. In addition, the inert gas will preferably be moistened upon contact (direct or indirect) with the basic solution referred to above or in a manner as described in WO-A-02/058885.

  According to an alternative embodiment of the invention, the part of polishing solution subjected to analysis by near-infrared spectroscopy (hereinafter referred to as NIR analysis) is preferably located before the first distribution point of the polishing solution to a polishing tool in the distribution loop of the solution.

  According to another variant of the invention, the polishing solution portion subjected to NIR analysis is located after the last distribution point of the polishing solution to a polishing tool. Of course, in general, one or more analyzes may be used in each of the preparation and / or distribution loops and the analysis points may be located at any point of the loop preferably at the beginning and / or at the end of the loop as explained above.

  According to another embodiment of the invention, the electromagnetic radiation NIR is emitted using at least one probe which is immersed in the polishing solution. The measurement will be carried out either by transmission, in which case a similar window will be necessary opposite to the first one on the pipe, or by reflection, in which case a mirror will have to be placed in the pipe opposite the window. This electromagnetic radiation NIR can for example be emitted through a window made of material transparent to said electromagnetic radiation, a window disposed on a polishing solution distribution pipe.

  The electromagnetic radiation can also be emitted through at least a portion of the polishing solution which is bypassed with respect to the main flow of the solution to its point of use. This is preferably to avoid possible problems of pollution of the solution by the probe itself.

  Preferably, the determination of the composition according to step c) of the process is carried out using a measuring apparatus of said composition, which apparatus is calibrated prior to the implementation of the method.

  According to a preferred variant of the invention, the calibration step of the measuring apparatus consists for a polishing solution containing n majority components and n 'minority components, to constitute a library of the NIR absorption spectra of at least 2 ("+" - different samples, the majority components being constituted by all the components whose concentration in the solution is greater than 1% vol., While the minority components are constituted by all the components whose concentration in the solution is less than 1% vol According to another variant of the process according to the invention, steps a) to e) are carried out on different parts of the polishing solution, taken sequentially.

  The invention also relates to a system for implementing the method described above. It relates more particularly to a system for measuring and / or controlling the composition of at least one polishing solution distributed in at least one polishing solution dispensing system for polishing semiconductor wafers during the manufacture of said semi-conductors. -conductors, characterized in that it comprises: a) a source of electromagnetic radiation emitting in the at least near-infrared range, in a wavelength range of at least 800 to 2100.10-9 m, b) means for directing the radiation emitted by this source on at least part of the at least one polishing solution; c) means for measuring the absorption spectrum of this electromagnetic radiation by transmission through and / or reflection by said part of the at least one polishing solution, d) means for performing a NIR spectroscopic analysis in the near infrared on the absorption spectrum of said radiation by said solution for determining the composition of at least one polishing solution, e) means for triggering the operation of the means a), b), c) and d) in a predetermined sequence.

  The system according to the invention will preferably comprise a light guiding device, preferably comprising at least one optical fiber, for conducting the electromagnetic radiation from its source substantially to the polishing solution.

  The system according to the invention may also include means for measuring and / or controlling the composition of one or more polishing solutions to perform a simultaneous or sequential measurement in several parts of one or more polishing solutions.

  Preferably, the system according to the invention will comprise means for continuously measuring and / or controlling the composition of at least one polishing solution.

  According to an alternative embodiment, the system according to the invention will comprise at least one immersible probe in the polishing solution, said probe being located at the end of the means for directing the radiation emitted by the source of electromagnetic radiation.

  Also preferably, the means d) above to perform a NIR analysis will comprise a memory for storing the absorption spectra of at least 2 (n + n ') -1 samples of a polishing solution comprising n components. majority and n 'minority components. In this case, such a system will comprise means for learning the determination of the composition of a polishing solution from a data library placed in a memory and representing spectra of polishing solution samples of known composition .

  The method and system according to the invention using NIR near-infrared spectroscopy type technology makes it possible to qualitatively monitor the presence of constituents of an on-line mixture in the process whether in the mixing drums or in the preparation loop of the polishing solution or in the loop or in the polishing solution dispensing drum. Such a method can be applied as soon as the reception of raw materials control. It allows a limitation of the stops of the distribution systems because the control is carried out upstream of the drums of mixture to prepare the solution of polishing. The method according to the invention can also be used for the qualification of the raw materials supplied to the customer before proceeding to the different formulations.

  Continuous monitoring of the quality of the mixture makes it possible to detect in real time a drift in the composition of the polishing solution, in the event of an incident in the preparation of the mixture or in the case of supply of poorly proportioned product, or discriminate polishing solutions other than those provided for with the type of circuit to be polished.

  The calibration required for the quantification of constituents using this technology must follow a precise methodology consisting in establishing a mathematical model based on the analysis of at least a number 2 (n + n ') -' of standard samples (known ) where the solution contains n majority and n 'minority constituents. To do this, the range of calibration of the apparatus for learning is determined initially from the average concentration curve for each of the components and its statistical distribution with a standard deviation a for each of said constituents, a curve which is provided by the semiconductor manufacturer and / or by the polishing solution manufacturer and resulting from his experience.

  The method according to the invention has a number of advantages and variants listed below: First of all no sample preparation is necessary prior to analysis. The concentrations of the various constituents (according to a preferred variant of the invention) can be measured in real time and continuously in the mixture. In addition, the measurement of the concentrations of the various constituents of the mixture can be carried out in a repeatable manner, that is to say that by carrying out the measurement on the same sample several times in succession, the same results are obtained. The calibration of the apparatus used for the measurements is important and although it is only a particular example of the invention, this calibration can be carried out statically in a manner adapted to the measurement of so-called diluted solutions, but also in dynamics.

  To do this, we first define a concentration range of calibration solutions adapted to each of the constituents, range called area of validity. In the context of the semiconductor manufacturing and the polishing of integrated circuit boards, the definition of this area of validity is based on the average curve established for each of the constituents relating to the measurement of the concentration of these constituents in the solutions achieved during the previous period (which may extend to a month or more) to obtain a statistical distribution of the concentration of each of the constituents with a mean value and a standard deviation a for each of them.

  Known concentration calibration solutions of the polishing solution are then prepared in the range of validity defined hereinafter. For a polishing solution which comprises n majority constituents, ie whose concentration in the solution is greater than 1% by volume, the range of validity can be up to 6 6, 6 being the standard deviation defined. above for each of the constituents. As regards the n 'minor constituents, ie those whose concentration varies between 0,1% by volume and 1% by volume, the range of validity is defined as ranging from -36 to + 6a by compared to the average concentration value defined above.

  The calibration solutions of the apparatus having known concentrations for each constituent of the mixture are then prepared in the range of validity defined above. At least 2 (n + "')"' samples are made whose spectrum is measured by the commercial apparatus used and this spectrum is stored in memory.

  Given that the composition of the sample is known, it is thus possible to assign to each spectrum the compositions of the corresponding majority or minority components.

  In this way, the intelligent system of the measuring apparatus NIR can, thanks to an algorithm known per se, make the learning of the determination of the measurement of the concentrations thanks to the 2 ("+" - 'samples at least entered in the memory With their corresponding composition, measurements can then be made consisting in measuring the spectrum of a sample in the appropriate domain and calculating the concentration of each of the constituents by means of the mathematical model carried out using the 2 ("+" - ' samples entered into memory.

  According to another aspect of the invention, it has been found that it is very important to avoid having particles or bubbles in the optical path, especially at the level of the analysis probe in the polishing solution bath, because the presence of gases in particular could completely distort the measurement and / or calibration. In order to avoid this kind of problem, it will be possible for example to ensure the continuous scanning of the probe by the mixture of polishing solution, to avoid the contamination of the mixture by the introduction of the probe, to avoid the contamination of the mixture due to corrosion / abrasion of the probe. The presence of gas bubbles in the optical path has the effect in particular of reducing by 50% or even more the absorption intensities which completely distorts the measurement.

  The invention will be better understood with the aid of the following exemplary embodiments, together with the figures, which represent: FIG. 1, an overall view of the polishing solution distribution system using a NIR analysis system according to FIG. FIG. 2 shows a first system for connecting the NIR probe in a polishing solution distribution loop; FIG. 3 is another system for connecting the NIR probe to any point of the distribution circuit.

  FIG. 1 diagrammatically shows a polishing solution distribution system according to the invention using an analysis and / or control system using a NIR near-infrared method according to the invention. In FIG. 1a, the preparation circulation loop of the polishing solution 1 circulates the polishing solution from the base of the mixing drum 8 to the upper part of said mixing drum 8. At the point 12 is connected a first capacitor containing deionized water for example pressurized with pressurized electronic purity nitrogen from a source 25 (not shown in the figure). This is generally the source of electron purity nitrogen present at the semiconductor manufacturing site consisting of pure nitrogen and dry.

  On the distribution loop 1 there are then n distribution capabilities of n different additives, all connected substantially in the same way on the loop. Thus the first capacitor 3 which receives its component from a feed shaft 31 connected at 18 is kept under pressure by the nitrogen 25 and the product is distributed at 13 in the distribution loop. Similarly, the component No. 2 is in the capacity 4 connected by the connection 14 to the loop 1, capacity pressurized by the nitrogen 25 and supplied at 19 by the No. 2 component from the drum 32. The component No 3 is connected at 15 to the dispensing line, the capacity 5 which contains it is fed through the compound No. 3 of the barrel 33 and dispensed under pressure with nitrogen 25, etc. The n- 'compound that arrives at 21 of the capacity 34 is dispensed into the capacity 6 maintained under pressure by the nitrogen 25 and dispensed into the polishing solution circulation line through the collection 16, while finally the nth The component received at 22 from capacity 35 provides the capacity 7 itself under nitrogen pressure 25 and distributes its component through line 17 in the circulation line 1.

  The analysis system according to the invention 10 is connected by line 11 to the circulation loop 1. The supply mode of this probe will be described in more detail later.

  In the mixing drum, the various ingredients of the polishing mixture of the polishing solution according to the invention are mixed by means of the helix 9, these various ingredients of the mixture consisting on the one hand by the present example the deionized water of the capacity 2 (but this can be a solvent or any other liquid) and the n additives in the capacities 3, 4, 5, .... 6, 7. The distribution of the polishing solution from the barrel in the distribution loop 101 as will be explained hereinafter, is carried out thanks to the pressurization with the nitrogen 25 (like all the other capacities described in this figure) and the pressure imposed by the Nitrogen on the solution in the mixing drum 8 upstream thereof in the pipe 98 which itself fills a dispensing drum 102 which constitutes a buffer capacity which feeds the distribution loop 101. This buffer capacity 102 is also pressurized g with the nitrogen 25 so as to distribute its solution through the pipe 101 under the action of the pressure of nitrogen on said solution which thus brings up this solution in the line 101 and the distribution in the lines 1011, 1012 and 1013 with three buffer delivery capacities respectively 104, 105 and 106 which are also pressurized under nitrogen 25, the distribution of the polishing solution in the loop 101 being carried out sequentially by pressurizing the nitrogen 25 successively above the capacitors 104, 105 and 106 so as to always distribute and preferably continuously distribution solution in the loop 101 fed respectively by the connections 1014, 1015 and 1016. When these buffer capacities 104, 105, 106 are empty the control system of the set (not detailed or explained in this figure) can fill via the distribution capacity probably successivem these buffers 104, 105, 106 when necessary. The polishing solution therefore circulates continuously in the loop 101 and preferably at the beginning of this loop at least one second NIR probe will be provided making it possible to analyze the spectrum and hence the composition of the solution prior to its distribution in the loop 2870344 12 which may comprise a large number of polishing solution distribution assemblies at the wafer polishing station which will be connected respectively at 107 and 108 to the continuous distribution loop 101. The return of the solution in the loop 101 is carried out via the pipe 97 to return to the distribution drum or 98 to return directly to the buffer capacities 104, 105 or 106.

  As explained above, FIG. 1b shows the n distribution systems of the n components which are mixed to produce the polishing solution (in addition to the deionized water or other constituent of the capacity 2). The 1 o component 1 in the capacity 31 is distributed as necessary by the nitrogen 25 which pressurizes the zone 41 above the component so as to distribute it to the connection point 18 described above with possible return of the surplus by the loop 51 in the drum 41. In the same way, we find for the components 2, 3, ..., n- ', n the same function for respectively 32, 33, ..., 34, 35; 42, 43, 44, 45; 19, 20, ..., 21, 22; 52, 53, ..., 54, 55; than the references respectively 31, 41, 18 and 51.

  FIG. 2 represents a first connection mode of the NIR probe in a distribution and recirculation loop of the polishing solution.

  The solution circulates continuously in the loop 202, 204, 201 composed of the lines 212, 211, 210 and 209, as well as in the line and the elements between the manual valves with minimum dead zone 205 and 208. This in order to avoid any stagnation zone conducive to sedimentation phenomena and thus maintain the homogeneity of the polishing solution. The flow rates in the different lines are balanced by the rolling valve 203. The determination of the composition of the polishing solution can therefore be carried out at any time in sequential or continuous mode. It is also possible to take a sample of the polishing solution by the valve 206 and thus have the possibility of controlling the composition of the polishing solution offline. This sampling line is systematically rinsed from the supply of deionized water 207 through the pneumatic valve 217.

  FIG. 3 represents another variant embodiment of FIG. 2.

  The solution circulates continuously in the recirculation loop 301 composed of lines 303 and 302. In this case, the composition of the polishing solution is measured in sequential mode. During the measurement, the pneumatic valve with minimum dead zone 304 opens and circulates the polishing solution through the manual valve 307 (for disassembly of the NIR probe if necessary) and the measuring cell NIR 308 until to the drain 309. After a delay necessary for the evacuation of the water initially present in the line and the measuring cell, the analysis can be performed. After the measurement is complete, the valve 304 is closed and the line is rinsed as a whole from the deionized water supply 305.

Claims (1)

  1. Method for measuring and / or controlling the composition of at least one polishing solution distributed by at least one polishing solution distribution system for polishing semiconductor wafers, 1) directing the electromagnetic radiation emitted by a source in the near-infrared range corresponding to a wavelength range of between 800 and 2100 x 10-9 on at least a part of the at least one polishing solution, 2) measuring the absorption spectrum of this electromagnetic radiation transmitted through and / or reflected by said part of the at least one polishing solution, 3) the composition of said at least one polishing solution is determined by spectroscopic analysis in the field of the near infrared or the radiation absorption spectrum by said solution, 4) if necessary, repeat steps 1) to 3) above, 5) determine possible changes in compositions of the polishing solution during the method of dispensing the polishing solution.   2. Method according to claim 1, characterized in that a light guide device, preferably comprising at least one optical fiber, is used to conduct the electromagnetic radiation from its source substantially to the polishing solution.   3. Method according to claim 1 or 2, characterized in that the point of use of the polishing solution is located at a distance from the place where said source of electromagnetic radiation is located.   4. Method according to one of claims 3, characterized in that the composition of the polishing solution of several networks or polishing solution distribution systems are measured and / or controlled simultaneously and / or sequentially.   5. Method according to one of claims 1 to 4, wherein is continuously carried out the measurement and / or control of the composition of the polishing solution.   6. Method according to one of claims 1 to 5, wherein a sample of polishing solution is extracted to transfer it to the place where it will be subjected to steps 1 to 3, possibly 4, of the process.   7. Method according to one of claims 1 to 6, wherein at least one polishing solution distribution system comprises a continuous distribution loop of the solution from a dispensing drum until the return in the barrel of the solution undistributed, this loop having at least one point of use of said solution.   8. Method according to one of claims 1 to 7, wherein the polishing solution is prepared by mixing additives to a base solution, the part of the polishing solution of step 2 of the process being a part of the polishing solution available after preparation.   9. Method according to claim 8, characterized in that the preparation of the polishing solution is carried out by mixing the additives in the mixing drum with the base solution and by circulating said solution thus prepared in a preparation loop in order to homogenize, until this solution is at least partially transferred into the distribution loop, the solution portion of step 2) of the process being a part of the preparation loop.   10. Method according to one of claims 1 to 9, characterized in that the portion of polishing solution subjected to NIR analysis is located before the first distribution point of the polishing solution to a polishing tool.   11. Method according to one of claims 1 to 10, characterized in that the polishing solution portion subjected to NIR analysis is located after the last distribution point of the polishing solution to a polishing tool.   12. Method according to one of the preceding claims, characterized in that the electromagnetic radiation NIR is emitted using at least one probe which is immersed in the polishing solution.   13. Method according to one of claims 1 to 12, characterized in that the electromagnetic radiation NIR is emitted through a window of material transparent to said electromagnetic radiation, disposed on a distribution pipe of the polishing solution.   Method according to one of claims 1 to 13, characterized in that the electromagnetic radiation is emitted through at least a portion of the polishing solution which is in the bypassing relation to the main flow of said solution to its point use.   15. Method according to one of claims 1 to 14, characterized in that the determination of the composition according to step 3) of the process is carried out with the aid of a measuring apparatus of said composition, which apparatus is calibrated prior to the implementation of said method.   16. The method of claim 15, characterized in that the prior calibration step of the measuring apparatus consists, for a polishing solution containing n major components and n 'minority components to constitute a library of NIR absorption spectra. at least 2 (n + n -1 different samples.   17. Method according to one of the preceding claims, characterized in that it carries out steps 1) to 5) on different parts of polishing solution taken sequentially.   A system for measuring and / or controlling the composition of at least one polishing solution dispensed in at least one polishing solution delivery system for polishing semiconductor wafers during the manufacture of said semiconductors, characterized in it includes: (a) a source of electromagnetic radiation emitting in the at least near-infrared range, in a wavelength range of at least 800 to 2100.10-9 m, (b) means for directing radiation emitted by this source on at least a part of the at least one polishing solution, c) means for measuring the absorption spectrum of this electromagnetic radiation by transmission through and / or reflection by said part of the at least one solution polishing; d) means for performing NIR spectroscopic analysis in the near infrared on the absorption spectrum of said radiation by said solution for determining the composition at least one polishing solution, e) means for triggering the operation of the means a), b), c) and d) according to a predetermined sequence.   19. System according to claim 18, characterized in that a light guide device, preferably comprising at least one optical fiber, is used to conduct the electromagnetic radiation from its source substantially to the polishing solution.   20. System according to one of claims 17 or 18, characterized in that it comprises means for measuring and / or controlling the composition of one or more polishing solutions to perform a simultaneous or sequential measurement in several parts. one or more polishing solutions.   21. System according to one of claims 18 to 20, characterized in that it comprises means for measuring and / or continuous control of the composition of at least one polishing solution.   22. System according to one of claims 18 to 21, characterized in that it comprises at least one immersible probe in the polishing solution, said probe being located at the end of the means for directing the radiation emitted by the source of electromagnetic radiation.   23. System according to one of claims 18 to 22, characterized in that the means d) for carrying out a NIR analysis comprise a memory for the storage of absorption spectra of at least 2 (n + n - 'samples'). a polishing solution comprising n major components and n 'minor components.   24. System according to one of claims 18 to 23, characterized in that it comprises learning means for determining the composition of a polishing solution from a data library placed in a memory and representing spectra of samples of polishing solution of known composition.