JP2008145102A - Method and device for inspecting foreign matter in semiconductor polishing slurry - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method and a device for inspecting foreign matter in a slurry, capable of inspecting the foreign matter such as an impurity particle contained in the semiconductor polishing slurry, and capable of acquiring precisely information about the foreign matter. <P>SOLUTION: This method of inspecting the foreign matter in the slurry has a sampling process of collecting the semiconductor polishing slurry, a dilution process of diluting the semiconductor polishing slurry collected in the sampling process, using a dispersant extracted from the semiconductor polishing slurry, a filtration process of passing and filtrating the diluted semiconductor polishing slurry, through a filtration membrane having 0.1 nm-100 μm of pore size capable of passing an abrasive grain contained in the semiconductor polishing slurry diluted in the dilution process, and capable of capturing the foreign matter larger than the abrasive grain, and a foreign matter inspection process of inspecting the foreign matter filtration-separated on a surface of the filtration membrane passed therethrough with the diluted semiconductor polishing slurry. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an inspection method and an inspection apparatus for foreign matters contained in a semiconductor polishing slurry, and particularly, in a slurry for inspecting foreign matters filtered on a filtration membrane by filtering the semiconductor polishing slurry through a filtration membrane. The present invention relates to a foreign matter inspection method and inspection apparatus.

  In the manufacture of a semiconductor device, it is required to flatten the surface of a semiconductor substrate to be used and the surface of a film formed thereon. For example, in order to form a semiconductor integrated circuit having a multilayer wiring layer in which wiring layers are three-dimensionally arranged, it is necessary to flatten the surface of an interlayer insulating film (such as a silicon oxide film or a silicon nitride film) between the multilayer wirings. is there.

  This is because when a silicon oxide film is formed by the CVD method after forming the first layer (lowermost layer) aluminum wiring, the surface of the silicon oxide film becomes uneven due to the presence of the wiring layer. In the etching process, if the second aluminum wiring layer is formed on the oxide film having the unevenness, there is a problem that the exposure focus of resist patterning is not focused on the uneven portion, or a dry etching residue is generated on the stepped portion. This is because it will occur.

  As a technique for flattening the surface of the film, a method of polishing the surface of the film using an abrasive is employed. In this method, polishing is performed by interposing a slurry between a polishing member such as a pad and a semiconductor substrate. As abrasive grains in the slurry used at this time, the dispersibility is good and the average particle diameter is uniform. For this reason, silica and alumina are generally used. Therefore, as the slurry, these abrasive grains are dispersed in a dispersion medium such as pure water, and an oxidizing agent such as hydrogen peroxide depending on the purpose. A special composition in which components such as a metal salt, an organic acid, and a dispersant are dissolved is used.

  When polishing is performed using such a slurry, the material forming the polishing surface of the semiconductor substrate is scraped off, and the abrasive grains themselves are crushed to generate polishing scraps. This polishing waste itself reduces the polishing power of the slurry. In addition, even if the slurry is diluted with a slurry stock solution and the concentration is adjusted for wafer polishing, the foreign particles such as impurity particles are not completely absent. In some cases, compounds are formed. Among these, large particle size polishing debris and agglomerates cause scratches on the substrate surface, and cause a reduction in polishing force due to accumulation of polishing debris (see, for example, Patent Document 1).

  Such foreign matter is probably because the abundance is very small compared to abrasive grains just by examining the particle size distribution of the particles in the slurry. Regardless, the existence of a peak could not be confirmed, which has been overlooked so far.

  Moreover, since it is confirmed that such a foreign substance is already contained in the adjustment stage in which the slurry stock solution is diluted and the concentration is adjusted for wafer polishing, the foreign substance contained in the slurry is not necessarily limited to processing waste. Rather, there may be several causes such as when it is already contained in the slurry stock solution or when substances falling from the inner wall of the tank or piping are mixed inside the polishing apparatus, but the cause of the mixing is Not sure.

As a method for inspecting foreign matter in the slurry, which can be inspected for foreign matters such as impurity particles contained in such a slurry, the slurry is passed through a filtration membrane, filtered, and the foreign matter in the slurry. A foreign matter inspection method has been attempted in which the presence or nature of foreign matter can be confirmed by capturing the product on a filtration membrane and directly subjecting the filtration membrane to inspection.
JP 2006-43781 A

  However, in the above method, foreign matter can be confirmed, but evaluation of the foreign matter is difficult, and further improvement in inspection accuracy is required.

  In view of the above circumstances, the present invention is capable of inspecting foreign matters such as impurity particles contained in such a semiconductor polishing slurry more accurately, and an inspection method and inspection of foreign matters in a semiconductor polishing slurry. An object is to provide an apparatus.

  That is, in the foreign matter inspection method according to an aspect of the present invention, a sampling step for collecting a semiconductor polishing slurry, and a semiconductor polishing slurry collected in the sampling step are diluted with a dispersion extracted from the semiconductor polishing slurry. A filtration process with a pore size of 0.1 nm to 100 μm that allows the abrasive grains contained in the polishing slurry for semiconductor diluted in the dilution process and the dilution process to pass therethrough and captures foreign matters larger than the abrasive grains. Inspecting foreign matter filtered and filtered on the surface of the filtration membrane obtained by passing the diluted polishing slurry for semiconductor, and passing through the diluted polishing slurry for semiconductor. A foreign matter inspection step.

  The foreign matter inspection method according to another aspect of the present invention includes a sampling step for collecting a semiconductor polishing slurry, and abrasive grains contained in the semiconductor polishing slurry collected in the sampling step, which are larger than the abrasive grains. Foreign matter can be trapped, the polishing slurry for semiconductor is passed through a filtration membrane having a pore diameter of 0.1 nm to 100 μm and filtered, and the polishing slurry for semiconductor obtained in the filtration step is passed through. Before inspecting the foreign matter filtered off on the surface of the filtered membrane, a cleaning step of washing the filtration membrane with a dispersion extracted from the polishing slurry for semiconductors in order to remove the abrasive grains remaining from the membrane. And a foreign matter inspection step of inspecting the foreign matter cleaned by the cleaning step.

  Furthermore, a foreign matter inspection apparatus according to another aspect of the present invention includes a sample collection unit that collects semiconductor polishing slurry from a semiconductor polishing slurry supply line, and abrasive grains contained in the semiconductor polishing slurry that pass through the abrasive grains. Large foreign matter can be captured, a filtration device having a filtration membrane with a pore diameter of 0.1 nm to 100 μm, and a semiconductor polishing slurry for transferring a semiconductor polishing slurry collected by a sample collection unit to the filtration device Slurry for supplying the dispersion extracted from the semiconductor polishing slurry to at least one of the transfer line and the semiconductor polishing slurry transfer line to which the semiconductor polishing slurry is transferred and the filtering device for filtering the semiconductor polishing slurry. It has a dispersion liquid supply means and an inspection unit for inspecting foreign matter filtered off on the surface of the filtration membrane.

  According to the present invention, foreign matter in a semiconductor polishing slurry can be confirmed with higher accuracy.

  Hereinafter, the foreign substance inspection method and foreign substance inspection apparatus in the slurry of the present invention will be described. First, the foreign matter inspection method in the slurry of the present invention will be described, but before that, the wafer polishing method using the slurry will be briefly described.

  In the wafer polishing, first, a necessary amount of slurry stock solution is supplied from a tank containing the slurry stock solution, and the slurry concentration is adjusted to a slurry concentration suitable for use in the polishing process while mixing the diluted solution with this stock solution. In the slurry used here, silica fine particles are often used as abrasive grains for reasons such as good dispersibility and uniform average particle diameter, and additives, for example, oxidation, are used in a dispersion medium such as water. It is general to use as a silica suspension (colloidal silica) in which the silica fine particles are dispersed by adding an agent, a metal salt, a dispersant and the like.

  Next, the silicon substrate held by the wafer carrier (packing agent) is rotated and pressed against the polishing pad while dripping the slurry whose concentration has been adjusted onto the polishing pad. Then, the silicon substrate is polished by rotation with the slurry interposed between the silicon substrate and the polishing pad, and the unevenness is removed from the insulating film formed on the surface of the silicon substrate by this polishing, and the surface becomes a flat surface. .

  The sampling step of the present invention may be sampled from any step of the wafer polishing method as described above. Specifically, the semiconductor polishing slurry stock solution or the semiconductor polishing slurry stock solution obtained by diluting the semiconductor polishing slurry stock solution and adjusting the concentration may be collected. Furthermore, the semiconductor polishing slurry stock solution may be collected from a bottle or the like before being stored in the tank of the wafer polishing apparatus.

  In the dilution step of the present invention, the semiconductor polishing slurry obtained by sampling is diluted with a dispersion liquid extracted from the semiconductor polishing slurry (hereinafter referred to as “slurry dispersion liquid”). Here, the slurry dispersion is a permeate obtained by filtering (removing) abrasive grains of solid polishing components and foreign matters larger than the abrasive grains with a film or the like. The slurry dispersion is preferably a solution obtained by removing the entire solid from the polishing slurry for semiconductor. In addition, when the components of the slurry are disclosed in a chemical substance safety data sheet (MSDS) or the like, the drug component or the like is artificially added to pure water to prepare a slurry dispersion liquid, and the film or the like is used as an abrasive. Also, large foreign substances may be removed and used. The removal of abrasive particles and foreign matters larger than the abrasive grains from the semiconductor polishing slurry, which produces the slurry dispersion used in this dilution step, is performed by filtration membranes such as ultrafiltration membranes, nanofiltration membranes, reverse osmosis membranes, precision It can be performed by filtration using a filtration membrane or by centrifugation using a centrifuge.

The filtration membrane for producing the slurry dispersion used in this dilution step can be used without particular limitation as long as it is a filtration membrane having a pore size capable of capturing abrasive grains and foreign matters larger than the abrasive grains from the semiconductor polishing slurry. However, a filtration membrane having a small pore size is preferable because it aims at removing abrasive grains having a relatively small particle size. As a filtration membrane with such a small pore size, ultrafiltration (UF) membrane (pore size: 2 to 100 nm), nanofiltration (NF) membrane (pore size: 0.5 to 2 nm), reverse osmosis (RO) membrane (pore size: 0.1-1 nm), microfiltration (MF) membrane (pore diameter: 0.1-100 μm), and the like. Examples of the ultrafiltration membrane (UF) include Microza (registered trademark) SEP-0013 (manufactured by Asahi Kasei Corporation). Examples of the reverse osmosis (RO) membrane include cross-linked polyamide composite membrane element TMG20-430 (manufactured by Toray Industries, Inc.). Examples of the microfiltration (MF) membrane include Nyukuripore membrane (manufactured by Nomura Micro Science Co., Ltd.).
Moreover, the filtration membrane used for this dilution process is formed with organic polymer etc., and can select a pore shape, a shape, and a usage method according to the property etc. of the grinding | polishing slurry for semiconductors used as object.

  The centrifuge for producing the slurry dispersion used in this dilution step is not particularly limited as long as it can separate abrasive grains and foreign matters larger than the abrasive grains from the semiconductor polishing slurry by centrifugation. . In addition, the type and use conditions of the centrifuge can be selected according to the properties of the target semiconductor polishing slurry.

  Note that the degree of dilution can be adjusted so that the diluted polishing slurry for semiconductor can be appropriately filtered in the filtration step of the present invention described later. In addition, the dilution process of this invention can be abbreviate | omitted when the extract | collected polishing slurry for semiconductors is a density | concentration etc. which can perform the below-mentioned filtration process without requiring dilution (concentration adjustment).

  As described above, since the semiconductor polishing slurry obtained by sampling is diluted with the slurry dispersion, as in the case of dilution with pure water, fluctuations in the pH of the slurry, additives in the slurry, such as oxidants, Aggregation of abrasive grains does not occur due to fluctuations in metal concentration, dispersant concentration, abrasive zeta potential, etc., so that the generation of abrasive agglomerates can be suppressed, and the form and properties of foreign matter can be changed. Without any change, that is, with respect to foreign matters in the slurry, the shape or the like does not change due to fluctuations in pH like the abrasive grains, additives in the slurry, such as fluctuations in the concentration of oxidizer or metal, fluctuations in the concentration of the dispersant, The foreign matter can be detected with higher accuracy as it is.

  In the filtration step of the present invention, the abrasive grains contained in the semiconductor polishing slurry are allowed to pass through, but the semiconductor polishing slurry diluted with the slurry dispersion is applied to a filtration membrane having a pore size that captures foreign matters larger than the abrasive grains. The liquid is passed through and filtered.

  The filtration membrane used in this step allows the abrasive grains in the semiconductor polishing slurry to pass therethrough, but foreign substances larger than the abrasive grains are not particularly limited as long as the filtration membrane has a pore size to be captured on the filtration membrane. Can do.

  The filtration membrane is formed of an inorganic or organic polymer or the like. Depending on the properties of the target slurry, a microfiltration (MF) membrane (pore size: 0.1 to 100 μm), an ultrafiltration (UF) membrane (pore size: 2 nm to 2 nm) 100 nm), nanofiltration (NF) membrane (pore diameter: 0.5 nm to 2 nm), reverse osmosis (RO) membrane (pore diameter: 0.1 nm to 1 nm), flat membrane, tubular membrane, hollow fiber membrane, etc. The usage method can be selected. Examples of the shape of the filtration membrane include a flat membrane shape, a roll shape, and a turret shape. When the shape of the filtration membrane is a roll shape or a turret shape, the filtration operation can be performed continuously (at regular intervals).

  The roll-shaped filtration membrane (filter roll) will be described in more detail with reference to FIGS. As shown in FIG. 1, a roll-shaped filtration membrane (filter roll) 1 is covered with a double-sided tape 3 except for a filtration portion 2 of the filter. The double-sided tape 3 has a circular portion corresponding to the filtration portion 2 cut out, and functions to prevent leakage of the semiconductor polishing slurry (sample liquid). As shown in FIG. 2, the filter roll 1 is designed to automatically feed the filter by being wound up by the filter roll take-up unit 4, and can continuously supply a new filtration part 2, so that it is continuously filtered. be able to. Filtration is performed by sucking from below the discharge funnel 7 using, for example, the filter 5 (comprising the cylinder 6 and the discharge funnel 7). The detector 8 inspects the foreign matter on the filter roll 1 sent out after the filtration operation.

Next, a turret-shaped filtration membrane will be described. As shown in FIG. 3, the turret-shaped filtration membrane 9 includes a filtration portion 10 that performs filtration and a protective film 11. The protective film 11 is produced by hollowing out a circular portion corresponding to the filtration portion 10 and prevents leakage of the semiconductor polishing slurry (sample liquid). As shown in FIG. 4, the turret-shaped filtration membrane 9 has a structure in which only the center portion is fixed by the fixing portion 12 and rotates like a record.
The semiconductor polishing slurry (sample solution) is filtered while the turret-shaped filtration membrane 9 is sandwiched between the cylinder 14 and the discharge funnel 15 constituting the filter 13. The filtered part that has been filtered rotates and the next new filtered part is supplied so that the filtration can be performed continuously. Filtration is performed, for example, by suction from below the discharge funnel 15. Foreign matter on the rotated turret-shaped filtration membrane 9 is inspected by the detector 16.

  The behavior of abrasive grains is greatly affected by fluctuations in the pH of the slurry, additives such as oxidizing agents, fluctuations in metal concentration, fluctuations in dispersant concentration, fluctuations in the zeta potential of abrasive grains, etc. Conceivable. Here, the zeta potential is a potential difference that occurs at the interface between the solid and the liquid that are in contact with each other when the relative motion is performed. If the absolute value of the zeta potential increases, the repulsion between the solids will occur. Become stronger.

  Therefore, when considering the case of abrasive grains as solids, the stability of the abrasive grains increases as the absolute value of the zeta potential increases, and the particles tend to aggregate as the absolute value of the zeta potential approaches zero. It is important to perform the filtration step without changing the slurry-containing composition components.

  After the filtration step, before the foreign matter inspection step, a washing step for washing the surface of the filtration membrane used in the filtration step with the slurry dispersion can be provided.

In this washing process, the surface of the filtration membrane is washed with the slurry dispersion, so that the fluctuation of the pH around the abrasive grains that occurs when pure water passes through the filtration membrane, as in the case of washing with pure water, A slurry additive around the grain, for example, oxidizing agent, fluctuation of metal concentration, fluctuation of dispersing agent concentration, fluctuation of zeta potential of abrasive grains, etc. will not cause aggregation of abrasive grains, so it remains on the membrane surface. The abrasive grains remaining on the filter membrane surface can be washed away without causing the abrasive grains to aggregate.
Also, when washing with pure water, when the pure water passes through the filter holes, the abrasive grains move (pulled) to the vicinity of the filter holes due to the movement of the pure water to the filter holes. Abrasive grains come closer to each other, and agglomeration of abrasive grains is more likely to occur, but by washing with a slurry dispersion, the abrasive grains are not agglomerated under such circumstances, that is, around the abrasive grains. It can be washed away in the absence of fluctuations in pH, slurry additives around abrasive grains and foreign matters, for example, oxidizing agent, metal concentration fluctuations, dispersant concentration fluctuations, and abrasive grain zeta potential fluctuations.

  That is, in the washing step, the surface of the filtration membrane is washed with the slurry dispersion, so that the abrasive grains remaining on the filtration membrane surface can be washed out without agglomerating the abrasive grains. Generation | occurrence | production can be suppressed and it can be set as the state which caught the foreign material made into test | inspection on the filtration membrane surface, and in a next foreign material inspection process, a foreign material can be detected more accurately.

  In this washing step, the slurry dispersion can be used in such an amount that the abrasive grains remaining on the filtration membrane can pass through the pores of the filtration membrane and leave foreign matters on the filtration membrane.

  Further, when necessary as a pretreatment for inspection in the next foreign substance inspection step, the filtration membrane surface can be further washed with pure water, and the dissolved component residue in the slurry can be washed away from the filtration membrane surface. In this case, since the abrasive grains are not left on the surface of the filtration membrane by washing with the slurry dispersion, the dissolved component residue in the slurry can be washed away by this pure water washing.

  Next, the foreign matter inspection step of the present invention is to inspect foreign matter captured on the surface of the filtration membrane obtained by passing the slurry diluted with the slurry dispersion obtained in the filtration step.

The foreign matter inspection step is not particularly limited as long as it is a method capable of inspecting the foreign matter on the surface of the filtration membrane. For example, observation of the presence, size, number, etc. of foreign matters using a scanning electron microscope (SEM). Examples of the foreign matter inspection method include observation of the presence / absence, size, number, etc. of foreign matter using a combination of an energy dispersive X-ray analyzer (EDX) and SEM, component analysis, and a method of detecting microorganisms. Further, a foreign matter inspection method such as measurement and analysis of the presence / absence, size, number, area, etc. of foreign matter using a combination of an image acquisition device and an image processing device may be mentioned.
Here, the inspection includes various methods for obtaining information about other foreign matters, such as confirmation of the presence / absence of foreign matter, confirmation of the shape and size of the foreign matter, analysis of the composition component of the foreign matter, and the like.

  An inspection method using a scanning electron microscope (SEM) is not particularly limited as long as it has sufficient resolution to observe pores and foreign matter on the surface of the filtration membrane. It is preferable to have the resolution to measure.

  A scanning electron microscope is an apparatus that irradiates an electron beam narrowly focused in a vacuum while scanning the surface of the sample, and observes an electron optical image of the electron beam reflected or transmitted from the surface of the sample on a cathode ray tube. Yes, when the sample is conductive to irradiate an electron beam, the irradiated electron accumulates and a correct image cannot be obtained. Therefore, a conductive thin film is formed on the surface to prevent the accumulation of electrons. There is a need. As a method for forming the conductive thin film, a vacuum deposition method and an ion sputtering method can be used.

  In this way, the filtration membrane covered with the conductive membrane on the filtration membrane is fixed to the sample stage, placed in the sample chamber, and measurement is performed. What is necessary is just to make it the magnification at the time of this measurement being 100-50000 times. When observing pores on the filtration membrane surface or foreign matters larger than the pores (minimum particle size of about 1 μm), it is preferably performed at a magnification of 100 to 10,000 times, observing the aggregation state of slurry particles, Or the like (minimum particle size of about 10 nm) is preferably performed at a magnification of 10,000 to 50,000 times.

  An inspection method performed by combining a scanning electron microscope and an energy dispersive X-ray analyzer (SEM-EDX) can perform component analysis by X-ray in addition to an inspection method by a scanning electron microscope. According to this, in addition to morphological observation, the composition component of the foreign matter can be analyzed together with its existence ratio, so that it is possible to inspect the origin of the foreign matter.

  Moreover, as a method for detecting microorganisms, a method for detecting fluorescence emitted when a microorganism is irradiated with a radiation light source, a colony formed by culturing microorganisms present on the surface of the filtration membrane by placing the filtration membrane on the medium as it is. The method of observing is mentioned. In the case of culturing, since the culture conditions differ depending on the type of microorganism and there are suitable media, temperature, etc., the conditions may be appropriately selected depending on the microorganism considered as a target.

  Further, a foreign matter inspection method using a combination of an image acquisition device and an image analysis device includes information on a foreign matter image on the surface of a filtration membrane, which is imaged using an image acquisition (imaging) device such as a CCD camera or a video camera. Using an image processing (analysis) apparatus (for example, product name: LUZEX (registered trademark) AP manufactured by NIRECO), the digital data is converted into digital data that can be digitally processed (from an electrical signal from a CCD camera, etc.) The presence / absence, size, number of foreign substances, area of each foreign substance and / or total area of foreign substances, etc. are measured and / or analyzed (calculated) by data calculation processing. In addition, when imaging the surface of a filtration membrane using an image acquisition (imaging) apparatus, for example, a CCD camera, it is preferable that the filtration membrane is sandwiched between transparent plates (for example, glass plates) and then flattened.

In addition, for example, when the aggregate of abrasive grains formed before dilution and cleaning is known in advance by the shape thereof, information (digital data) of such aggregates of abrasive grains is imaged. Foreign matter can be easily determined by removing it from the digital data of (image) information captured by the apparatus by differential processing or the like. For example, only foreign matter can be displayed on the monitor of the image processing apparatus. it can. In addition, if there is something whose type and shape of the foreign substance are known in advance, the digital type of the foreign substance and the digital data of the (image) information imaged by the imaging device are compared to determine the type of foreign substance. It can also be specified. Information (digital data) of such known agglomerates of abrasive grains and known foreign matter is stored in a data memory section of an image processing (analysis) device, and is captured by these digital data and an imaging device ( Image) The foreign matter may be inspected by comparing with digital data of information.
In this foreign matter inspection method, an image of the foreign matter is picked up by an imaging means such as a CCD camera, so that the cleaning process with pure water on the surface of the filtration membrane, which is a pretreatment necessary for the vapor deposition processing of the scanning electron microscope, is omitted. can do.

Next, the foreign matter inspection apparatus of the present invention will be described. Items already described in the inspection method for foreign matter are omitted.
FIG. 5 is a diagram showing an example of the configuration of the main part of the foreign matter inspection apparatus of the present invention. This foreign matter inspection apparatus includes a sample collection unit 21 for collecting a semiconductor polishing slurry, a semiconductor polishing slurry transfer line 22 for transferring the collected semiconductor polishing slurry to a filtration device, and a semiconductor to which the semiconductor polishing slurry is transferred. The slurry dispersion supply means 23 for supplying the slurry dispersion and the abrasive grains contained in the semiconductor polishing slurry are allowed to pass through the polishing slurry transfer line for semiconductor and / or the filtration device in which the semiconductor polishing slurry is filtered. A filtering device 24 capable of catching foreign matters larger than the grains and an inspection unit 25 for inspecting the foreign matters are provided. In FIG. 5, the foreign matter inspection apparatus includes a sample tank 26 for storing the collected semiconductor polishing slurry, a filtrate adjusting tank 27 for diluting (preparing) the collected semiconductor polishing slurry to a predetermined concentration, and for the collected semiconductor. There is provided pure water supply means 28 for supplying pure water for diluting the polishing slurry to a predetermined concentration and / or washing the filtration device (filter membrane) after filtering the semiconductor polishing slurry.

  The sample collection unit 21 collects the semiconductor polishing slurry from the semiconductor polishing slurry supply line. The sample collection unit 21 includes, for example, a sample tube and a pump (not shown) for collecting (introducing) the semiconductor polishing slurry from the semiconductor polishing slurry supply line. When the pressure of the semiconductor polishing slurry supply line is sufficient to introduce the semiconductor polishing slurry into the sample tube, the pump (not shown) can be omitted. Further, for example, by controlling the opening and closing of the valve (for example, automatic control), the semiconductor polishing slurry can be collected (introduced) continuously or at regular intervals. The semiconductor polishing slurry collected by the sample collection unit 21 is transferred to the sample tank 26.

  The semiconductor polishing slurry transfer line 22 transfers the semiconductor polishing slurry in the sample tank 26 to the filtration device 24 via the filtrate adjustment tank 27 using, for example, a pump. The semiconductor slurry is adjusted (diluted) to a concentration suitable for filtration in the filtrate adjustment tank 27 when the concentration needs to be adjusted (diluted). The concentration can be adjusted with a slurry dispersion or (ultra) pure water, but it is preferable to dilute with a slurry dispersion as described above, since aggregation of abrasive grains does not occur.

The slurry dispersion supply device 23 includes a filtration film for removing foreign particles larger than abrasive grains and abrasive grains from the semiconductor polishing slurry supplied from the sample tank 26, and foreign particles larger than abrasive grains and abrasive grains are removed. The slurry dispersion is supplied to the filtrate adjustment tank 27. Moreover, the slurry dispersion supply device 23 supplies the slurry dispersion to the filtration device 24 (on the filtration membrane) after the semiconductor polishing slurry is filtered. By supplying the slurry dispersion to the filtration device, foreign substances filtered off on the filtration membrane, that is, removal of abrasive grains remaining on the filtration membrane can be performed.
The solution containing abrasive grains and foreign matters larger than the abrasive grains after the slurry dispersion liquid is extracted by the slurry dispersion supply apparatus 23 is returned to the sample tank 26 or discharged out of the system. When returning to the sample tank 26, the concentration of the semiconductor polishing slurry in the sample tank 26 increases, but the inspection can be performed without discharging foreign matter or the like in the collected semiconductor polishing slurry. Note that the slurry dispersion supply device 23 does not directly supply the obtained slurry dispersion to the filtrate adjustment tank 27 and / or the filtration device 24 after filtering the semiconductor polishing slurry, but in advance the slurry dispersion tank ( The slurry dispersion can be supplied from a slurry dispersion tank.

  The filtration device 24 has a filtration membrane 29 having a pore diameter of 0.1 nm to 100 μm that allows the abrasive grains contained in the semiconductor polishing slurry to pass therethrough and capture foreign substances larger than the abrasive grains. The polishing slurry for semiconductor transferred from the liquid adjustment tank 27 is filtered. Moreover, the filtration apparatus 24 is equipped with the hole (not shown) for extracting the air after introduce | transducing the polishing slurry for semiconductors. The filtration device 24 filters the semiconductor polishing slurry by suction, for example, by a suction unit, for example, a vacuum pump (not shown).

  The inspection unit 25 inspects the foreign matter filtered off on the surface of the filtration membrane. As described above, the foreign matter is inspected (observed) using a combination of a scanning electron microscope, an imaging device, and an image processing device.

  The sample tank 26 stores the collected semiconductor polishing slurry. The filtrate adjusting tank 27 can be used to dilute the semiconductor polishing slurry transferred from the semiconductor polishing slurry transfer line 22 with a slurry dispersion or (ultra) pure water to an appropriate concentration.

  The pure water supply means 28 can supply pure water to the filtrate adjustment tank 27 in order to dilute the semiconductor polishing slurry and adjust it to a concentration suitable for filtration. Further, the pure water supply means 28 removes the remaining abrasive grains from the foreign matter on the filtration membrane 29 in the filtration device 24 after filtering the semiconductor polishing slurry, so that the filtration membrane 29 of the filtration device 24 is removed. Pure water can be supplied to the top. The pure water supply means 28 can also supply ultrapure water instead of pure water.

  Note that the foreign substance inspection apparatus of the present invention controls (for example, automatically controls) the opening and closing of each valve shown in FIG. 5 and adjusts (for example, synchronizes) the timing of opening and closing of each valve. Thus, the steps up to filtration can be automatically (continuously) performed in the inspection of foreign matters. Further, by collecting the semiconductor polishing slurry in the sample collection unit 21 at regular intervals, it is possible to periodically inspect foreign matters. Furthermore, the foreign matter in the inspection unit can be continuously (periodically) inspected by making the filtration membrane in the filtration device into a roll shape or a turret shape.

  In addition, the foreign matter inspection method and foreign matter inspection apparatus of the present invention can be used for any purpose intended to inspect foreign matter in a semiconductor polishing slurry. For example, it can be used for inspection of foreign matters in the slurry in the storage state of the semiconductor polishing slurry, inspection of foreign matters in the semiconductor polishing slurry during operation of the wafer polishing apparatus, and the like. Among these, since it can be used for inspection of foreign matters in a semiconductor polishing slurry during operation of a wafer polishing apparatus, quality control during polishing of the semiconductor can be performed, and scratches on the substrate surface can be prevented in advance. preferable.

  Hereinafter, the present invention will be described in detail by way of examples and comparative examples.

(Comparative Example 1) New liquid 1
First, a conventional method will be described as Comparative Example 1. A holder was set with a Nukuripore membrane filter (trade name: Nycrypore Polycarbonate, Track Etch Membrane) with a pore size of 3.0 μm, 5 mL of pure water was collected in a syringe and injected from the top of the holder to remove air. Air venting is performed in order not to cause uneven filtration.

  Next, a semiconductor polishing slurry (new solution) containing silica having a particle size of 141 to 337 nm (manufactured by Cabot Microelectronics Corporation, trade name: Semi-Space W2000) and having a silica concentration of 3 to 10% before being used for wafer polishing. ) Was taken into a syringe (1 mL) and pure water (9 mL), and these were mixed and diluted 10-fold in the syringe, and 10 mL of this diluted slurry was set on the top of the holder and filtered by hand.

  After filtration of the diluted slurry, 50 mL of pure water was supplied to the membrane filter with a syringe and filtered to wash the filter surface. As a result, the slurry-dissolving component (for example, an oxidant, an additive such as a metal, and a dispersant) was washed and removed from the filter surface, and foreign matters of 3 μm or more were captured on the surface.

  Next, the filter in which the foreign matter was captured on the surface was fixed to the SEM sample stage with double-sided tape, and Pt- was applied to the filter surface with an ion sputtering apparatus (trade name: Hitachi Mild Sputter E-1030, manufactured by Hitachi High-Technologies Corporation). Pd vapor deposition was performed so that the film thickness was 30 mm. The surface of this filter was observed with a scanning electron microscope (SEM; manufactured by Hitachi High-Technologies Corporation, trade name: S-4100 type) at a magnification of 1000 times. A photograph showing the result is shown in FIG. As shown in FIG. 6, the filter is provided with a large number of holes 31 having a diameter of 3.0 μm. On the filter, abrasive grains 32 that have not been removed by cleaning, aggregates 33 of abrasive grains previously formed by aggregation before dilution and cleaning, and abrasive grains aggregated by dilution and / or cleaning with pure water are provided. It was confirmed that there were aggregates 34 (abrasive aggregate 34a by pure water dilution, abrasive aggregate 34b by pure water cleaning) and foreign matter 35.

  In this way, it was confirmed that the foreign matter 35 that could not pass through the hole 31 was captured on the surface of the filter, but in addition to the previously formed aggregate 33 of abrasive grains, polishing for semiconductors was performed. When the abrasive grain component in the slurry is diluted with pure water and / or contacted with pure water by washing the filter surface after filtration, the pH of the slurry varies, and the additives in the slurry (for example, oxidizing agents, metals, etc.) ) Concentration fluctuation, abrasive zeta potential fluctuation, pH fluctuation around the abrasive grains, slurry additives around the abrasive grains, eg, oxidizer, metal concentration, dispersion fluctuation, etc. It was also confirmed that particles larger than the filter pore diameter, that is, agglomerates 34 of the abrasive grains, were present on the filter. Therefore, in this method, it is difficult to distinguish between the foreign matter 5 and the abrasive aggregates 33 and 34 in the semiconductor polishing slurry. Moreover, when the component analysis of the foreign material 35 was performed with an energy dispersive X-ray analyzer (manufactured by EDX Japan Co., Ltd.), it was C, O, Si, and it was confirmed that the foreign material was derived from the slurry component. .

(Example 1)
In this example, first, preparation of a slurry dispersion for diluting a semiconductor polishing slurry will be described. First, the same semiconductor polishing slurry as used in Comparative Example 1 before being used for wafer polishing was converted into a pencil-type ultrafiltration module (manufactured by Asahi Kasei Co., Ltd., trade name: Microza (registered trademark), model SEP. -0013, pore diameter: 2 nm), a permeate (slurry dispersion) from which abrasive grains and foreign matter components larger than the abrasive grains were removed from the semiconductor polishing slurry was obtained.

  Next, set the holder to the same 3.0 μm pore diameter membrane filter as used in Comparative Example 1 above, collect 5 mL of the slurry dispersion in a syringe, and inject it from the top of the holder to remove air. It was. Air venting is performed in order not to cause uneven filtration. In this operation, 5 mL of pure water is used to vent the air, and after the air venting is completed, at least 10 mL of the slurry dispersion liquid is added, and the pH on the membrane filter and the liquid components in the holder may be equivalent to the slurry.

  Next, the semiconductor polishing slurry before being used for the same wafer polishing as described above is taken into a syringe (1 mL) and a slurry dispersion (9 mL), and these are mixed and diluted 10 times in a syringe, and 10 mL of this diluted slurry is added. It was set on the top of the holder and filtered by hand.

  After filtration of the diluted polishing slurry for semiconductor, 50 mL of the slurry dispersion was supplied to the membrane filter with a syringe and filtered to discharge out of the holder without agglomerating the abrasive grains on the membrane filter. Then, in order to prevent the corrosion at the time of the vapor deposition process of Pt-Pd for observation with a scanning electron microscope on the filter surface, 50 mL of pure water was supplied with a syringe and filtered, and the filter surface was washed. By this washing, the slurry-dissolved component remaining on the filter surface was removed, and foreign matters were captured on the surface.

  Next, the filter on which the foreign matter was trapped on the surface was fixed to the SEM sample stage with double-sided tape, and Pt—Pd was vapor-deposited on the filter surface by an ion sputtering apparatus in the same manner as in Comparative Example 1. The surface of this filter was observed with a scanning electron microscope at a magnification of 500 times. A photograph showing the results is shown in FIG. As shown in FIG. 7, on the filter provided with a large number of holes 31 having a diameter of 3.0 μm, agglomerates 33 and foreign matter 35 that have been pre-aggregated before dilution and cleaning are confirmed. However, agglomerates 34 of abrasive grains that agglomerate by dilution and / or washing with abrasive grains 32 and pure water could not be confirmed. Therefore, it was confirmed that the foreign matter 35 can be easily determined.

(Comparative Example 2) New solution 2
In this comparative example, an experiment was performed using a new polishing slurry for semiconductors different from that in Comparative Example 1 and Example 1.

  Dilution operation and filtration using a polishing slurry for semiconductor having a silica concentration of 10 to 30% containing silica having a particle diameter of 50 to 400 nm (trade name: SS25, manufactured by Cabot Microelectronics Corporation) before being used for wafer polishing Operations, cleaning operations, observation of the filter surface and photographing were performed in the same manner as in Comparative Example 1. A photograph showing the result is shown in FIG. As shown in FIG. 8, it was confirmed that foreign matter 35 that cannot pass through the hole was captured on the filter surface, but it was agglomerated in advance before dilution and washing. In addition to the abrasive agglomerates 33, it is confirmed that there are abrasive grains 32 that have not been removed by washing, and agglomerates 34 (34a, 34b) that agglomerate by dilution and / or washing with pure water. It was. Therefore, in this method, it is difficult to distinguish between the foreign matter 35 and the abrasive aggregates 33 and 34 in the semiconductor polishing slurry.

(Example 2)
A polishing slurry for a semiconductor having a silica concentration of 10 to 30% and containing silica having a particle size of 50 to 400 nm (product name: SS25, manufactured by Cabot Microelectronics Corporation) before being used for wafer polishing is converted into a reverse osmosis filtration module (Toray Industries, Inc.). A permeate (slurry dispersion) obtained by removing abrasive grains and foreign matter components larger than the abrasive grains from the semiconductor polishing slurry using a cross-linked polyamide composite membrane element manufactured by Co., Ltd., model TMG20-430, pore size: 1 nm) Obtained.

  Next, in the same manner as in Example 1, dilution operation, filtration operation, washing operation, observation and photographing of the filter surface were performed in the same manner as in Example 1. A photograph showing the results is shown in FIG. As shown in FIG. 9, the aggregate 33 and foreign matter 35 of the abrasive grains that had been agglomerated before the dilution and cleaning were confirmed on the filter, but diluted with the abrasive grains 32 and pure water and / or Aggregates 34 of abrasive grains that aggregate by washing could not be confirmed. Therefore, it was confirmed that the foreign matter 35 can be easily determined.

It is a figure which shows typically a roll-shaped filtration membrane (filter roll). It is a figure which shows typically an example of the principal part structure of the filtration part using a roll-shaped filtration membrane (filter roll). It is a figure which shows typically a turret-shaped filtration membrane. It is a figure which shows typically an example of the principal part structure of the filtration part using a turret-shaped filtration membrane. It is a figure which shows an example of the principal part structure of the foreign material inspection apparatus of this invention. 6 is a photograph showing the state of a filter surface observed with a scanning electron microscope in Comparative Example 1. 2 is a photograph showing the state of the filter surface observed with a scanning electron microscope in Example 1. FIG. 6 is a photograph showing the state of a filter surface observed by a scanning electron microscope in Comparative Example 2. 6 is a photograph showing the state of a filter surface observed with a scanning electron microscope in Example 2. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Roll-shaped filtration membrane (filter roll), 2,10 ... Filtration part, 3 ... Double-sided tape, 4 ... Filter roll winding-up part, 5,13 ... Filter, 6,14 ... Cylinder, 7,15 ... Discharge Use funnel 8, 16 ... detector, 9 ... turret-shaped filtration membrane, 11 ... protective film, 12 ... fixing part, 21 ... sampling part, 22 ... polishing slurry transfer line for semiconductor, 23 ... slurry dispersion supply means , 24 ... Filtration device, 25 ... Inspection section, 26 ... Sample tank, 27 ... Filtrate adjustment tank, 28 ... Pure water supply means, 29 ... Filtration membrane, 31 ... (filter) hole, 32 ... Granulation, 33 ... Agglomerated aggregates (formed before dilution and washing) 34... Agglomerated aggregates (formed by dilution and / or washing with pure water) 34 a. Agglomerates, 34b ... pure water wash Lab particle agglomerates formed by, 35 ... foreign matter.

Claims (8)

A sampling process for collecting a polishing slurry for semiconductor;
A dilution step of diluting the polishing slurry for semiconductor collected in the sampling step with a dispersion extracted from the polishing slurry for semiconductor;
Abrasive grains contained in the polishing slurry for semiconductor diluted in the dilution step are allowed to pass through, and foreign substances larger than the abrasive grains can be captured, and the dilution is applied to a filtration membrane having a pore diameter of 0.1 nm to 100 μm. A filtration step of passing and filtering the polished slurry for semiconductor,
A foreign matter inspection method for inspecting foreign matter filtered off on the surface of the filtration membrane through which the diluted polishing slurry for semiconductor obtained through the filtration step is passed. .   Before inspecting the foreign matter obtained in the filtration step, the method has a step of washing the filtration membrane with a dispersion extracted from a semiconductor polishing slurry in order to remove abrasive grains remaining from the filtration membrane. The method for inspecting foreign matter in a slurry according to claim 1. A sampling process for collecting a polishing slurry for semiconductor;
Abrasive grains contained in the semiconductor polishing slurry collected in the sampling step are allowed to pass through, and foreign substances larger than the abrasive grains can be captured, and the semiconductor has a pore diameter of 0.1 nm to 100 μm. A filtration step of passing and filtering a polishing slurry for use,
In order to remove the abrasive particles remaining from the filtration membrane before inspecting the foreign matter filtered off on the surface of the filtration membrane through which the polishing slurry for semiconductor obtained through the filtration step has been passed, the filtration membrane A washing step of washing with a dispersion extracted from a semiconductor polishing slurry;
And a foreign matter inspection step for inspecting the foreign matter cleaned by the cleaning step.   The dispersion liquid extracted from the semiconductor polishing slurry is obtained by filtering the semiconductor polishing slurry using a filtration membrane selected from a microfiltration membrane, an ultrafiltration membrane, and a reverse osmosis membrane or using a centrifuge. The method for inspecting foreign matter in a slurry according to any one of claims 1 to 3, wherein the foreign matter is in a slurry.   5. The slurry according to claim 1, wherein the shape of the filtration membrane having a pore diameter of 0.1 nm to 100 μm is any one of a flat membrane shape, a roll shape, and a turret shape. Foreign substance inspection method.   The method for inspecting foreign matter in a slurry according to any one of claims 1 to 5, wherein the inspection of the foreign matter in the foreign matter inspection step is performed by a scanning electron microscope.   6. The slurry according to claim 1, wherein the inspection of the foreign matter in the foreign matter inspection step is performed by an image processing unit that performs image processing on an image of the foreign matter captured by the imaging unit. Foreign substance inspection method. A sample collection section for collecting the semiconductor polishing slurry from the semiconductor polishing slurry supply line;
A filtration device having a filtration membrane with a pore diameter of 0.1 nm to 100 μm, which allows abrasive grains contained in a semiconductor polishing slurry to pass therethrough and captures foreign matters larger than the abrasive grains;
A polishing slurry transfer line for semiconductor that transfers the polishing slurry for semiconductor collected by the sample collection unit to the filtration device;
Slurry dispersion for supplying a dispersion extracted from the semiconductor polishing slurry to at least one of the semiconductor polishing slurry transfer line through which the semiconductor polishing slurry is transferred and a filtration device in which the semiconductor polishing slurry is filtered. Liquid supply means;
A foreign matter inspection device in a slurry, comprising: an inspection unit for inspecting foreign matter filtered off on the surface of the filtration membrane.