JP2012156181A - Cleaning liquid for semiconductor substrate and cleaning method using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cleaning liquid for a semiconductor substrate, which efficiently removes contamination without damaging the surface of a substrate after having been subjected to a CMP step of polishing a silicon oxide film and exposing a polysilicon film when the polishing step has finished, and to provide a cleaning method of the semiconductor substrate using the same.SOLUTION: The substrate is adjusted, which has a polysilicon film and the silicon oxide film that covers at least one part of a polysilicon layer, and the silicon oxide film is polished by using a CMP polishing liquid containing polishing particles until at least one part of the polysilicon layer is exposed to the outside. The cleaning liquid for the semiconductor substrate is a cleaning liquid which cleans the face having been polished of the substrate, and includes a nonionic surfactant having at least one acetylenic linkage in a molecule, and water.

Description

  The present invention relates to a semiconductor substrate cleaning liquid and a semiconductor substrate cleaning method using the same. More specifically, the present invention relates to a cleaning method including a step of polishing a substrate and cleaning foreign matter adhering to the substrate after polishing.

  In the field of semiconductor manufacturing, CMP (Chemical Mechanical Polishing) technology is one of the most important technologies for manufacturing a device in which wirings are multilayered. The CMP technique is a technique for flattening the surface by forming a thin film of various materials on a substrate by chemical vapor deposition (CVD) or the like and then polishing it using a CMP polishing liquid.

For example, planarization processing by CMP is indispensable for ensuring the depth of focus of lithography. If the surface of the substrate is uneven, there will be inconveniences such as inability to focus in the exposure process and the inability to sufficiently form a fine wiring structure. Further, in the CMP process, in the device manufacturing process, a step of forming an element isolation region by polishing a plasma oxide film (BPSG, HDP-SiO ₂ , p-TEOS), a step of forming an interlayer insulating film, or a silicon oxide It is also applied to a step of flattening a plug (for example, an Al / Cu plug) after embedding a film containing copper in a metal wiring.

  For example, in the process of forming an element isolation region, a technique with a narrow element isolation width is required as the processing dimension becomes finer, and STI (Shallow Trench Isolation) is being used. In STI, CMP is used to remove an extra silicon oxide film formed on a silicon substrate. For the purpose of preventing the silicon oxide film from being excessively polished, a process in which a stopper film is previously formed under the silicon oxide film and polishing is terminated when the stopper film is exposed is the mainstream. Generally, silicon nitride is used for the stopper film. In this case, the CMP polishing liquid desirably has a sufficiently high polishing rate ratio between the silicon oxide film and the stopper film.

  In recent years, in order to improve processing accuracy after CMP and to ensure flatness, a polysilicon film capable of controlling the polishing rate to be smaller is often employed as a stopper film. Actually, an additive capable of controlling the polishing rate of the cerium oxide polishing liquid, suppressing the polishing rate of polysilicon, and ensuring a sufficient polishing rate ratio compared to the polishing rate of the silicon oxide film is known ( For example, see Patent Document 1).

  By the way, on the surface of the substrate after CMP, in particular, on the polysilicon film, a foreign substance generally called contamination may remain. Examples of such contamination include abrasive particles contained in the CMP polishing liquid and polishing debris generated by polishing. As semiconductors are highly integrated, there is a high possibility that defects will occur in product performance even with a small amount of foreign matter on the substrate surface. For this reason, higher contamination control is required.

  Various methods for removing the contamination generated by the CMP process on the semiconductor substrate have been studied, and for example, an alkaline cleaning solution using ammonia or surface etching with dilute hydrofluoric acid has been proposed (for example, non-patent literature) 1).

International Publication No. 07/055278 Pamphlet

“Hydrogen Peroxide Solutions for Silicon Wafer Cleaning”, RCA Engineer, 28 (4), p9 (1983)

  However, when an alkaline cleaning liquid using ammonia is used, there is a problem that the removal efficiency of contamination is poor. On the other hand, the cleaning method using dilute hydrofluoric acid has higher removal efficiency of contamination compared with the cleaning method using an alkaline cleaning solution, but it is an etching removal, and thus has an adverse effect such as roughening of the substrate surface state. There is a fear.

  In addition, the present inventors have used a CMP polishing liquid using an additive for maintaining flatness after polishing, particularly when cerium oxide particles are used as abrasive grains. And found that removal was more difficult when polished.

  The present invention is intended to solve the above-described problem, and a semiconductor that polishes a silicon oxide film and efficiently removes contamination without roughening the substrate surface after the CMP process in which the polysilicon film is exposed when the polishing is completed. It is an object of the present invention to provide a substrate cleaning solution and a method for cleaning a semiconductor substrate using the same.

  As a result of intensive studies to solve the above problems, the present inventors have found that a high contamination removal efficiency can be achieved by cleaning a substrate using a cleaning liquid mainly composed of a compound having a specific structure. I found it.

  That is, according to the present invention, a substrate having a polysilicon film and a silicon oxide film covering at least a part of the polysilicon layer is prepared, and a CMP polishing liquid containing abrasive particles is used to prepare at least one of the polysilicon layer. Polishing the silicon oxide film until a portion is exposed, and cleaning the polished surface of the substrate, the cleaning liquid comprising at least one acetylene bond in the molecule, water, It is related with the washing | cleaning liquid for semiconductor substrates characterized by including.

  By cleaning with such a semiconductor substrate cleaning solution, particularly the silicon oxide film is polished, and almost all contamination is removed without roughening the substrate surface after the CMP process in which the polysilicon film is exposed when the polishing is completed. It becomes possible.

  Although the cause of this effect is not necessarily clear, the present inventors consider as follows. That is, it is considered that the contamination is attached to the substrate surface by being electrically attracted to the polysilicon film. Here, when washed with a cleaning liquid containing a nonionic surfactant (nonionic compound) having an acetylene bond, the nonionic compound has a property of adsorbing to both the polysilicon film and the abrasive particles. It is considered that the film becomes electrically neutral and the surface of the abrasive particles becomes electrically greatly negative. For this reason, it is presumed that the abrasive particles can be easily peeled off from the polysilicon film, and the re-adsorption to the silicon oxide film, which is electrically negative, is also suppressed, and high contamination removal characteristics are exhibited. The

  Here, the nonionic surfactant having at least one acetylene bond in the molecule contained in the cleaning liquid is represented by the following general formula (I):

(In general formula (I), R ¹ represents a hydrogen atom or a substituted or unsubstituted alkyl group having 1 to 5 carbon atoms, and R ² represents a substituted or unsubstituted alkyl group having 4 to 10 carbon atoms.) Or a compound represented by the following general formula (II)

(In General Formula (II), R ^{3 to} R ⁶ each independently represents a hydrogen atom or a substituted or unsubstituted alkyl group having 1 to 5 carbon atoms, and R ⁷ and R ⁸ each independently represents 1 to 1 carbon atoms. 5 represents a substituted or unsubstituted alkylene group, and m and n each independently represents 0 or a positive number. Thereby, contamination can be more efficiently removed.

  In the cleaning liquid, it is preferable that the abrasive particles dispersed in the cleaning liquid have a zeta potential of −60 mV or less. Thereby, contamination can be removed more efficiently, and reattachment to the substrate surface can be more efficiently suppressed.

  The pH of the cleaning liquid is preferably 4.0 or more and 8.0 or less. Thereby, the surface potential of the cerium oxide particles can be largely controlled negatively without causing the cleaning liquid itself to roughen the substrate surface.

  In the cleaning liquid for a semiconductor substrate of the present invention, the CMP polishing liquid preferably contains cerium oxide particles as polishing particles, and further contains a polyacrylic acid compound and water. Thereby, it becomes possible to stop the polishing with the polysilicon film while obtaining a good polishing rate for the silicon oxide film, and it is possible to suppress the contamination from remaining on the polished surface.

  Further, in the semiconductor substrate cleaning liquid of the present invention, the CMP polishing liquid is a CMP polishing liquid used by mixing the first liquid and the second liquid, and the first liquid includes cerium oxide particles, It is preferable that it contains a dispersant and water, and the second liquid contains a polyacrylic acid compound and water. The polyacrylic acid compound has an effect of stopping polishing in the polysilicon film and improving the flatness, but when added in a large amount, it may cause aggregation and sedimentation of cerium oxide particles. However, such a problem can be avoided by adopting the above configuration. There is also an advantage that the polishing rate can be easily adjusted and controlled.

  It is preferable that the polyacrylic acid compound is added to the CMP polishing liquid in such an amount that the polishing speed of the silicon oxide film is 30 times or more faster than the polishing speed of the polysilicon film.

  In the CMP polishing liquid, it is preferable that the second liquid further contains a surfactant. This has the effect of making it easier to stop polishing with the polysilicon film.

  The cleaning solution for a semiconductor substrate of the present invention fills the substrate having the irregularities formed thereon, the polysilicon film covering the convex portions of the substrate, the concave portions of the substrate, and covers the substrate surface as the substrate. It is preferable to have a silicon oxide film provided. By polishing such a substrate, it is possible to take advantage of the contamination removal efficiency, the polishing rate to the silicon oxide film, and the polishing stop property of the polysilicon film, which are the advantages of the cleaning method of the present invention. In this respect, it is preferable to polish the silicon oxide film of the substrate using the CMP polishing liquid until the polysilicon film covering the convex portions of the substrate is exposed.

  In the cleaning method, the polished substrate is pressed against a cleaning cloth on a surface plate for cleaning, and the substrate and the cleaning cloth are placed while supplying the semiconductor substrate cleaning liquid between the substrate and the cleaning cloth. It is preferable to clean the abrasive particles adhering to the substrate by relatively moving. As another method, the cleaning is preferably performed by cleaning the abrasive particles adhering to the substrate using a cleaning brush while supplying the semiconductor substrate cleaning liquid to the polished substrate. Thereby, contamination can be removed more efficiently. More preferably, the cleaning method of the present invention further includes a step of removing droplets adhering to the substrate after the cleaning.

  ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to provide the semiconductor substrate cleaning liquid and cleaning method which can remove the contamination (abrasive particle | grains and polishing waste) which arose on the wafer surface after a CMP process, especially a polysilicon film.

The schematic diagram which shows one Example of the board | substrate sectional drawing used by this invention, and the state which grind | polished the board | substrate.

  According to the present invention, a substrate having a polysilicon film and a silicon oxide film covering at least a part of the polysilicon layer is prepared, and at least a part of the polysilicon layer is obtained using a CMP polishing liquid containing abrasive particles. The silicon oxide film was polished until it was exposed, and the substrate was polished with a cleaning solution containing a nonionic surfactant (nonionic compound) having at least one acetylene bond in the molecule and water. The present invention relates to a semiconductor substrate cleaning liquid and a cleaning method using the same, characterized by cleaning a surface. Hereinafter, preferred embodiments of the present invention will be described in detail.

<Cleaning solution for semiconductor substrate>
The cleaning liquid for a semiconductor substrate according to the present embodiment contains a nonionic surfactant having at least one acetylene bond in the molecule and water.
As such a nonionic surfactant, the following general formula (I)

(In general formula (I), R ¹ represents a hydrogen atom or a substituted or unsubstituted alkyl group having 1 to 5 carbon atoms, and R ² represents a substituted or unsubstituted alkyl group having 4 to 10 carbon atoms.) And a compound represented by the following general formula (II)

(In General Formula (II), R ^{3 to} R ⁶ each independently represents a hydrogen atom or a substituted or unsubstituted alkyl group having 1 to 5 carbon atoms, and R ⁷ and R ⁸ each independently represents 1 to 1 carbon atoms. 5 represents a substituted or unsubstituted alkylene group, and m and n each independently represents 0 or a positive number. It is preferable that at least one selected from the group consisting of compounds represented by: Thereby, contamination can be more efficiently removed. Examples of the substituted or unsubstituted alkyl group having 1 to 5 carbon atoms in the general formulas (I) and (II) include a methyl group, an ethyl group, a propyl group, an iso-propyl group, a butyl group, an iso-butyl group, Examples thereof include a sec-butyl group, a tert-butyl group, a pentyl group, an iso-pentyl group, a neo-pentyl group, and a tert-pentyl group. Examples of the substituted or unsubstituted alkyl group having 4 to 10 carbon atoms include a butyl group, a pentyl group, a hexyl group, an octyl group, a nonyl group, and a decyl group. Examples of the substituted or unsubstituted alkylene group having 1 to 5 carbon atoms include an ethylene group, a propylene group, a butylene group, and a pentylene group.

  Specific examples of the nonionic surfactant represented by the general formula (I) include 1-decyne, 2-decyne, 3-decyne, 4-decyne, and 5-decyne.

  Specific examples of the nonionic surfactant represented by the general formula (II) include 2,4,7,9-tetramethyl-5-decyne-4,7-diol, 2,4,7. , 9-tetramethyl-5-decyne-4,7-diol, 2,4,7,9-tetramethyl-5-decyne-4,7-diol-dipolyoxyethylene ether, 2,4 , 7,9-tetramethyl-5-decyne-4,7-diol-monopolyoxyethylene ether.

  The addition amount of the nonionic surfactant having an acetylene bond is preferably 0.01% by mass or more, more preferably 0.05% by mass or more based on the total mass of the cleaning liquid, from the viewpoint of efficiently removing contamination. 0.10 mass% or more is more preferable. Although there is no restriction | limiting in particular in an upper limit, Generally 10 mass% or less is preferable.

  In the cleaning liquid, it is preferable that the abrasive particles dispersed in the cleaning liquid have a zeta potential of −60 mV or less. Thereby, there exists a tendency which can remove a contamination efficiently and can suppress the re-adsorption | suction of the abrasive particle to a polysilicon film. In this respect, the zeta potential is more preferably −65 mV or less, and further preferably −70 mV or less.

The lower limit of the pH of the cleaning liquid is preferably 4.0 or more, more preferably 4.5 or more, from the viewpoint of making the zeta potential of the abrasive particles alone negative and facilitating the adsorption of particles to the polysilicon film. 5.0 or more is more preferable. The upper limit of the pH of the cleaning liquid of the present invention is preferably 9.0 or less, more preferably 8.5 or less, from the viewpoint of contamination removal performance. 8.0 or less is more preferable.
Since the pH of the cleaning liquid may vary depending on the type of compound used as the nonionic surfactant, a pH adjusting agent may be added to the additive in order to adjust the pH to the above range. The pH adjuster is not particularly limited, and examples thereof include acids such as nitric acid, sulfuric acid, hydrochloric acid, phosphoric acid, boric acid and acetic acid, bases such as sodium hydroxide, aqueous ammonia, potassium hydroxide and calcium hydroxide. Can be mentioned. In addition, from the viewpoint of improving productivity, a cleaning solution may be prepared without using a pH adjuster and applied as it is.

<Polishing liquid>
(Abrasive particles)
The CMP polishing liquid used in the semiconductor substrate cleaning liquid and cleaning method of the present invention is preferably a polishing liquid containing cerium oxide particles.
The cerium oxide particles can be obtained, for example, by oxidizing a cerium compound such as carbonate, nitrate, sulfate, or oxalate. The cerium oxide particles used for polishing a silicon oxide film formed by the TEOS-CVD method or the like can be polished at a higher speed as the crystallite diameter of the particles is larger and the crystal distortion is smaller, that is, the better the crystallinity is. There is a tendency for polishing scratches to easily enter the polished film.

  The production method of the cerium oxide particles is not particularly limited, but the crystallite diameter is preferably 1 to 400 nm. The crystallite diameter can be measured by a TEM photograph image or an SEM image.

  As a method for producing the cerium oxide particles described as an example of the cerium oxide particles, for example, firing or an oxidation method using hydrogen peroxide or the like can be used. The firing temperature is preferably 350 to 900 ° C.

  When the cerium oxide particles are aggregated, it is preferably mechanically pulverized. As the pulverization method, for example, dry pulverization using a jet mill or the like, or wet pulverization using a planetary bead mill or the like is preferable. As the jet mill, for example, those described in “Chemical Engineering Papers”, Vol. 6, No. 5, (1980), pp. 527-532 can be used.

  Such cerium oxide particles are dispersed in water as a dispersion medium to obtain a cerium oxide slurry. As a dispersing method, for example, a homogenizer, an ultrasonic disperser, a wet ball mill, or the like can be used in addition to the dispersion treatment with a normal stirrer, using a dispersant described later.

  As a method for further micronizing the cerium oxide dispersed by the above method, for example, a sedimentation classification method is used in which the cerium oxide slurry is forcibly settled after centrifuging with a small centrifuge and only the supernatant liquid is taken out. Can do. In addition, a high-pressure homogenizer that collides the cerium oxide particles in the dispersion medium with each other at high pressure may be used.

  The average particle diameter of the cerium oxide particles in the slurry thus prepared is preferably 0.01 to 2.0 μm, more preferably 0.08 to 0.5 μm, and further 0.08 to 0.4 μm. preferable. When the average particle size is less than 0.01 μm, the polishing rate tends to gradually decrease. When the average particle size exceeds 2.0 μm, the film to be polished tends to be easily damaged by polishing.

  The average particle diameter of cerium oxide particles refers to the median diameter of volume distribution measured with a laser diffraction particle size distribution meter. Specifically, it is obtained using LA-920 (trade name) manufactured by Horiba, Ltd.

  The concentration of the cerium oxide particles is preferably 0.2 to 3.0% by mass, more preferably 0.3 to 2.0% by mass, based on 100% by mass of the entire CMP polishing liquid. More preferred is 1.5% by mass. When the concentration of the cerium oxide particles exceeds 3.0% by mass, the effect of adjusting the polishing rate by the additive liquid tends to be small. Moreover, when the concentration of the cerium oxide particles is less than 0.2% by mass, the polishing rate of the silicon oxide film tends to decrease, and a desired polishing rate tends not to be obtained.

(water)
The water used for the cleaning liquid and the polishing liquid is not particularly limited, but deionized water, ion exchange water or ultrapure water is preferable. If necessary, polar solvents such as ethanol, acetic acid, and acetone may be used in combination with water.

(Polyacrylic acid compound)
The CMP polishing liquid used in the present invention preferably contains a polyacrylic acid compound. Examples of the polyacrylic acid compound include acrylic acid polymers, and acrylic acid polymers include, for example, acrylic acid polymers and ammonium salts thereof, methacrylic acid polymers and ammonium salts thereof, and ammonium acrylate salts and alkyl acrylates. And a copolymer with (methyl, ethyl or propyl). Of these, polyacrylic acid ammonium salt or a copolymer of ammonium acrylate salt and methyl acrylate is preferred. When the latter is used, the molar ratio of ammonium acrylate salt to methyl acrylate is preferably 10/90 to 90/10 for ammonium acrylate salt / methyl acrylate. When the molar ratio of the ammonium acrylate salt to methyl acrylate is less than 10 or more than 90, the dispersibility tends to be not maintained.

Moreover, it is preferable that the weight average molecular weights of an acrylic acid polymer are 1000-20000. When the weight average molecular weight of the acrylic polymer exceeds 20000, the particle size distribution tends to change over time due to reagglomeration of the abrasive particles. When the weight average molecular weight is less than 1000, the dispersibility of the cerium oxide particles and the effect of preventing sedimentation are insufficient. There is.
Here, the weight average molecular weight is a value measured by gel permeation chromatography (GPC) and converted using a standard polystyrene calibration curve.
In general, the blending amount of the polyacrylic acid compound is preferably in the range of 0.01 to 5 parts by mass with respect to 100 parts by mass of the abrasive particles from the viewpoint of dispersibility of the abrasive particles in the polishing liquid and anti-settling property. . When the blending amount of the polyacrylic acid compound is less than 0.01 parts by mass, the abrasive particles are likely to settle, and the particle size distribution is likely to change with time due to reaggregation of the abrasive particles exceeding 5 parts by mass.

(Dispersant)
As the dispersant used in the present invention, the content of alkali metals such as sodium ions and potassium ions, halogens, and sulfur is preferably 10 ppm or less. For example, water-soluble organic polymers such as polyvinyl alcohol, ammonium lauryl sulfate, Water-soluble anionic surfactants such as polyoxyethylene lauryl ether ammonium sulfate, water-soluble nonionic surfactants such as polyoxyethylene lauryl ether and polyethylene glycol monostearate, and monoethanolamine, diethanolamine, N, N-diethyl Examples include water-soluble amines such as ethanolamine, N, N-dimethylethanolamine, and aminoethylethanolamine, and water-soluble organic polymers such as polyvinyl alcohol and polyvinylpyrrolidone.

  Further, the blending amount of the dispersant is preferably in the range of 0.01 to 5 parts by mass with respect to 100 parts by mass of the abrasive particles from the viewpoint of dispersibility of the abrasive particles in the abrasive and anti-settling property. When the blending amount of the dispersant is less than 0.01 parts by mass, the abrasive particles are likely to settle, and the particle size distribution is likely to change with time due to reaggregation of the abrasive particles exceeding 5 parts by mass.

  In order to enhance the dispersion effect of the dispersing agent on the abrasive particles, it is preferable to place the dispersing agent in the disperser simultaneously with the abrasive particles during the dispersion treatment.

The CMP polishing liquid used in the present invention preferably contains cerium oxide particles as abrasive particles, and further contains a polyacrylic acid compound and water. Thereby, it becomes possible to stop the polishing with the polysilicon film while obtaining a good polishing rate for the silicon oxide film, and it is possible to suppress the contamination from remaining on the polished surface.
The CMP polishing liquid used in the present invention is a CMP polishing liquid used by mixing the first liquid and the second liquid, and the first liquid contains cerium oxide particles, a dispersant, and water. It is preferable that the second liquid contains a polyacrylic acid compound and water. And it is preferable that the second liquid further contains a surfactant. The polyacrylic acid compound has an effect of stopping polishing in the polysilicon film and improving the flatness, but when added in a large amount, it may cause aggregation and sedimentation of cerium oxide particles. However, such a problem can be avoided by adopting the above configuration. There is also an advantage that the polishing rate can be easily adjusted and controlled.

(Surfactant)
In addition to the surfactants exemplified in the above-mentioned dispersant, the surfactant to be contained in the second liquid includes anionic surfactants, nonionic surfactants, cationic surfactants, and zwitterionic surfactants. A surfactant is contained alone or in combination of two or more, and a nonionic surfactant is particularly preferable.
Examples of the anionic surfactant include lauryl sulfate triethanolamine, ammonium lauryl sulfate, polyoxyethylene alkyl ether sulfate triethanolamine, and a special polycarboxylic acid type dispersant.
Nonionic surfactants include, for example, polyoxypropylene, polyoxyethylene alkyl ether, polyoxyethylene alkyl ether, polyoxyethylene alkyl allyl ether, polyoxyethylene polyoxypropylene ether derivatives, polyoxypropylene glyceryl ether, polyethylene Ether type surfactants such as oxyethylene adducts of glycol, methoxypolyethylene glycol, acetylenic diol, ester type surfactants such as sorbitan fatty acid ester and glycerol borate fatty acid ester, and amino ether type interfaces such as polyoxyethylene alkylamine Activator, polyoxyethylene sorbitan fatty acid ester, polyoxyethylene glycerol borate fatty acid ester, polyoxyethylene alkyl Ether ester type surfactants such as stealth, fatty acid alkanolamides, alkanolamide type surfactants such as polyoxyethylene fatty acid alkanolamides, oxyethylene adducts of acetylenic diols, polyvinylpyrrolidone, polyacrylamide, polydimethylacrylamide, etc. It is done.
Examples of the cationic surfactant include coconut amine acetate and stearylamine acetate.
Examples of amphoteric surfactants include betaine, β-alanine betaine, lauryl betaine, stearyl betaine, lauryl dimethylamine oxide, 2-alkyl-N-carboxymethyl-N-hydroxyethylimidazolinium betaine, amidopropyl betaine laurate. , Coconut oil fatty acid amidopropyl betaine, lauryl hydroxysulfobetaine and the like.

  The content of the surfactant is preferably 0.01 to 1.0% by mass, more preferably 0.02 to 0.7% by mass, and 0.03 to 0.5% by mass with respect to the entire CMP polishing liquid. Is more preferable. When the content of the surfactant exceeds 1.0% by mass, it leads to a decrease in the polishing rate of the silicon oxide film, which is not preferable. When the content of the surfactant is less than 0.01% by mass, This leads to an increase in the polishing rate, which is not preferable.

  The pH of the CMP polishing liquid is preferably 4.5-10. If the pH is less than 4.5, particles tend to aggregate, and if it exceeds 10, the polishing rate stability tends to deteriorate. Examples of the method for adjusting the pH of the CMP polishing liquid include a method of adding an alkaline substance not containing metal ions such as aqueous ammonia during or after the dispersion treatment.

<Polishing method>
In the polishing method used in the present invention, a substrate having a polysilicon film and a silicon oxide film covering at least a part of the polysilicon layer is prepared, and a CMP polishing liquid containing abrasive particles is used to form the polysilicon layer. The silicon oxide film is polished until at least a part of the silicon oxide film is exposed.

The method for polishing a substrate is to press the substrate on which a film to be polished is pressed against a polishing cloth on a polishing surface plate and apply pressure between the polishing film and the polishing cloth while supplying the CMP polishing liquid between the polishing cloth and the polishing plate. Move relative to polish the film.
Although there is no restriction | limiting in particular as abrasive cloth, It is preferable to use a general nonwoven fabric, a polyurethane foam, a porous fluororesin, etc. Further, it is preferable that the polishing cloth is subjected to groove processing so that an abrasive is collected.
The polishing conditions are not limited, but the rotation speed of the surface plate is preferably low rotation of 100 min ⁻¹ or less so that the substrate does not jump out, and the pressure applied to the substrate is 1 kg / cm so that polishing scratches do not occur after polishing. ² or less is preferable.
In order to move the polishing cloth and the film to be polished relatively with the polishing film on the substrate pressed against the polishing cloth, specifically, at least one of the substrate and the polishing surface plate may be moved. In addition to rotating the polishing surface plate, polishing may be performed by rotating or swinging the holder. Further, a polishing method in which a polishing surface plate is rotated on a planetary surface, a polishing method in which a belt-like polishing cloth is moved linearly in one direction in the longitudinal direction, and the like can be mentioned. The holder may be in any state of being fixed, rotating and swinging. These polishing methods can be appropriately selected depending on the surface to be polished and the polishing apparatus as long as the polishing cloth and the film to be polished are moved relatively. During polishing, a CMP polishing liquid is continuously supplied to the polishing cloth with a pump or the like. Although there is no restriction | limiting in this supply amount, it is preferable that the surface of polishing cloth is always covered with polishing liquid. Specifically, it is preferable to supply 0.02 to 0.25 ml per 1 cm ^{2 of} the polishing pad area.

  Here, as the substrate, as shown in the upper diagram of FIG. 1, the substrate 1 on which irregularities are formed, the polysilicon film 2 covering the projections of the substrate 1, and the recesses of the substrate 1 are filled, And the board | substrate which has the silicon oxide film 3 provided so that the base-material surface might be coat | covered is mentioned. Using the CMP polishing liquid, the silicon oxide film 3 of the substrate is polished until the polysilicon film 2 covering the convex portions of the substrate 1 is exposed, and is polished to the state shown in the lower diagram of FIG.

<Semiconductor substrate cleaning method>
Next, the polished substrate is cleaned using the semiconductor substrate cleaning solution. As a cleaning method, the substrate after polishing is pressed against a cleaning cloth on a surface plate for cleaning, while the cleaning liquid is supplied between the substrate and the cleaning cloth, the substrate and the cleaning cloth are moved relatively, A method for cleaning the abrasive particles adhering to the substrate is mentioned. As another cleaning method, there is a method of cleaning abrasive particles adhering to the substrate using a cleaning brush while supplying the cleaning liquid to the substrate after polishing. These methods may be performed alone or in combination.

In the cleaning method of the present invention, the polished wafer is pressed against a cleaning cloth on a cleaning surface plate, and the wafer and the cleaning cloth are relatively moved while supplying the cleaning liquid between the wafer and the cleaning cloth. When performing the wafer cleaning method of moving and cleaning the abrasive particles adhering to the wafer, it can be performed using a general polishing apparatus. Specifically, the apparatus includes a holder for holding a substrate and a polishing surface plate to which a cleaning cloth (pad) can be attached and a motor or the like whose rotation speed can be changed is attached. For example, polishing apparatus (model number: EPO-111, EPO-222, F _* REX200, F _* REX300) manufactured by Ebara Manufacturing Co., Ltd. ) Etc. can be used. As the cleaning cloth, a non-woven fabric, foamed polyurethane, porous fluororesin, and the like used in a general CMP process can be used, but a soft pad is more preferable than a hard pad from the viewpoint of polishing scratches. Further, it is preferable that the cleaning cloth is grooved so that the cleaning liquid is accumulated. Although there are no restrictions on the cleaning conditions, the rotation speed of the surface plate is preferably a low rotation of 200 rpm or less so that the semiconductor substrate does not jump out, and the pressure (working load) applied to the semiconductor substrate is 100 kPa or less so that scratches do not occur after cleaning. Is preferred. During cleaning, the cleaning liquid is continuously supplied to the cleaning cloth with a pump or the like. The supply amount is not limited, but it is preferable that the surface of the cleaning cloth is always covered with the cleaning liquid.

  It is preferable that the method further includes a step of removing droplets attached to the substrate after the cleaning. The abrasive particles can be efficiently removed by using a method of cleaning the abrasive particles adhering to the substrate using a cleaning brush while supplying the cleaning liquid to the polished substrate. After such a process, for example, there is a method of drying while removing droplets adhering to the substrate using spin dry, IPA (isopropyl alcohol) vapor or the like. More specifically, for example, the above Reflexion polishing machine It is possible to use the cleaning equipment associated with the etc.

  As a substrate in the cleaning method of the present invention, an inorganic insulating film on a semiconductor substrate such as a substrate related to semiconductor element manufacture, for example, a semiconductor substrate at a stage where a circuit element and a wiring pattern are formed, a semiconductor substrate at a stage where a circuit element is formed, etc. A substrate on which is formed. The surface to be cleaned includes the inorganic insulating film such as a silicon oxide film layer and a polysilicon film layer. By cleaning the silicon oxide film layer and the polysilicon film layer formed on such a semiconductor substrate with the above cleaning liquid, abrasive particles contained in the polishing liquid adhered to the wafer surface, such as cerium oxide particles and polishing scraps, etc. Contamination can be removed, and the surface of the semiconductor substrate can be smooth without any contamination.

  The cleaning method of this embodiment is suitable for cleaning a substrate having a silicon oxide film and a polysilicon film on the surface in the following device manufacturing process. Devices include, for example, individual semiconductors such as diodes, transistors, compound semiconductors, thermistors, varistors, thyristors, DRAMs (Dynamic Random Access Memory), SRAMs (Static Random Access Memory), EPROMs (Erasable Programmable)・ Read-only memory (ROM), mask ROM (mask read-only memory), EEPROM (electrically erasable programmable read-only memory), storage elements such as flash memory, microprocessor, DSP, ASIC, etc. Theoretical circuit elements, integrated circuit elements such as compound semiconductors represented by MMIC (monolithic microwave integrated circuit), hybrid integrated circuits (hybrid IC), light emitting diodes Such a photoelectric conversion element such as a charge coupled device and the like.

  EXAMPLES Hereinafter, although an Example demonstrates this invention still in detail, this invention is not limited to these Examples.

(Preparation of cleaning solution)
Example 1
As a nonionic surfactant having at least one acetylene bond in the molecule, 1.0 g of polyethoxylate of 2,4,7,9-tetramethyl-5-decyne-4,7-diol and 99.0 g of water were used. A mixed and adjusted substrate cleaning solution was obtained.

(Comparative Example 1)
25 mass% ammonia water was diluted 100 times to prepare 0.25 mass% ammonia water.

(Comparative Example 2)
100 g of water was prepared.

(Measurement of pH of cleaning solution and zeta potential of particles in cleaning solution)
A known cerium oxide polishing liquid (nonvolatile content NV = 4.0% by mass) and the prepared cleaning liquid were mixed at a ratio of 1: 3 (mass ratio), and then centrifuged for 10 minutes at a rotation speed of 8000 rpm in a centrifuge. After that, the supernatant liquid was measured using a zeta potential measurement: Zetasizer 3000HSA (Malvern). The pH was measured using a pH meter. The measurement results are summarized in Table 1.

(Adhesion of polishing liquid particles to silicon oxide film and polysilicon film and its confirmation method)
A known cerium oxide polishing liquid (non-volatile content NV = 4.0% by mass) and a known additive for increasing the polishing rate ratio of silicon oxide film / polysilicon film were mixed in a ratio of 1: 1 (mass ratio). Each of the following (1) silicon oxide film wafer piece and (2) polysilicon film wafer piece was immersed in the solution for 60 seconds, and then immersed in a container containing pure water for 30 seconds, and the wafer surface was blown with nitrogen. Was dried. The wafer piece thus obtained was observed at two arbitrary locations at a magnification of 20000 using a scanning electron microscope. The observation visual field was 6 μm × 4 μm, and the number of particles observed in the visual field range was counted. At this time, the number of particles of 0.1 μm or more that can be clearly recognized as particles was counted. The number of particles was defined as the number of particles attached to each film before cleaning with the cleaning liquid.
As the silicon oxide film wafer piece of (1), a wafer in which a PE-TEOS (plasma-enhanced tetraethyl-orthosilicate) silicon oxide film is formed to a thickness of 1000 nm on a Si substrate is sized vertically and horizontally (1 cm × 1 cm). The cut one was used. As the polysilicon film wafer piece (2), a wafer in which a PE-TEOS silicon oxide film having a thickness of 100 nm is formed on a Si substrate and a polysilicon film having a thickness of 100 nm is vertically and horizontally (1 cm). What was cut into a size of × 1 cm) was used.

(Adhesion of polishing liquid particles to silicon oxide film and polysilicon film and evaluation method for cleaning properties thereof)
Since it was confirmed that the particles adhered to the silicon oxide film and the polysilicon film by the above-described method, the cleaning performance was confirmed using a cleaning liquid. In a liquid prepared by mixing a known cerium oxide polishing liquid (non-volatile content NV = 4.0% by mass) and an additive for increasing the polishing rate ratio of a known silicon oxide film / polysilicon film in a mixture of 1: 1 ( 1) Silicon oxide film wafer piece and (2) Polysilicon film wafer piece were each immersed for 60 seconds, then immersed in the prepared cleaning solution for 30 seconds, then immersed in a container containing pure water for 30 seconds, and then blown with nitrogen The wafer surface was dried. The wafer piece thus obtained was observed at two arbitrary locations at a magnification of 20000 using a scanning electron microscope. The observation visual field was 6 μm × 4 μm, and the number of particles observed in the visual field range was counted. At this time, the number of particles of 0.1 μm or more that can be clearly recognized as particles was counted. The number of particles was defined as the number of particles attached to each film after being cleaned with the cleaning liquid. The measurement results are summarized in Table 2.

(Evaluation results)
From Example 1 and Comparative Examples 1 and 2, it was shown that the cleaning liquid of the present invention is effective for removing adhered particles in both the silicon oxide film and the polysilicon film.

  The inventor has described the best mode for carrying out the invention in the specification. When the above description is read by a person skilled in the art, preferred variants similar to these may become apparent. The present inventors are fully aware of the implementation of different forms of the present invention as well as the implementation of similar forms of the invention to which the foundation of the present invention is applied. Moreover, the present invention can use, as its principle, all variations of the contents listed in the claims of the patent scope, and any combination of various elements described above. All possible combinations thereof are included in the invention unless otherwise specified herein or otherwise clearly denied by context.

1 ... Substrate 2 ... Polysilicon film (polysilicon layer)
3. Silicon oxide film

Claims (13)

Adjusting a substrate having a polysilicon film and a silicon oxide film covering at least a part of the polysilicon layer;
Using a CMP polishing liquid containing abrasive particles, the silicon oxide film is polished until at least a portion of the polysilicon layer is exposed, and the surface of the substrate that has been polished is cleaned.
A cleaning liquid for a semiconductor substrate, characterized in that the cleaning liquid contains a nonionic surfactant having at least one acetylene bond in the molecule and water. A nonionic surfactant having at least one acetylene bond in the molecule is represented by the following general formula (I):

(In general formula (I), R ¹ represents a hydrogen atom or a substituted or unsubstituted alkyl group having 1 to 5 carbon atoms, and R ² represents a substituted or unsubstituted alkyl group having 4 to 10 carbon atoms.) Or a compound represented by the following general formula (II)

(In General Formula (II), R ^{3 to} R ⁶ each independently represents a hydrogen atom or a substituted or unsubstituted alkyl group having 1 to 5 carbon atoms, and R ⁷ and R ⁸ each independently represents 1 to 1 carbon atoms. 5. A cleaning solution for a semiconductor substrate according to claim 1, wherein the compound is a compound represented by 5: a substituted or unsubstituted alkylene group, wherein m and n each independently represents 0 or a positive number.   The semiconductor substrate cleaning liquid according to claim 1, wherein the abrasive particles dispersed in the substrate cleaning liquid have a zeta potential of −60 mV or less.   The semiconductor substrate cleaning solution according to any one of claims 1 to 3, wherein the pH of the semiconductor substrate cleaning solution is 4.0 or more and 8.0 or less.   The cleaning liquid for a semiconductor substrate according to any one of claims 1 to 4, wherein the CMP polishing liquid is a polishing liquid containing cerium oxide particles as polishing particles, and further containing a polyacrylic acid compound and water.   The CMP polishing liquid is a CMP polishing liquid used by mixing the first liquid and the second liquid, and the first liquid contains cerium oxide particles, a dispersant, and water, and the second liquid The semiconductor substrate cleaning liquid according to claim 5, wherein the liquid contains a polyacrylic acid compound and water.   7. The polyacrylic acid compound is added to the CMP polishing liquid in an amount capable of polishing the silicon oxide film at a rate of 30 times or more faster than the polishing rate of the polysilicon film. Cleaning solution for semiconductor substrates.   8. The cleaning liquid for a semiconductor substrate according to claim 6, wherein the second liquid further contains a surfactant in the CMP polishing liquid.   The substrate has a base on which irregularities are formed, a polysilicon film covering the convex part of the base, and a silicon oxide film provided so as to fill the concave part of the base and cover the surface of the base It is a semiconductor substrate, The cleaning liquid for semiconductor substrates as described in any one of Claims 1-8.   The semiconductor substrate cleaning liquid according to claim 9, wherein the substrate is a semiconductor substrate obtained by polishing a silicon oxide film of the substrate using a CMP polishing liquid until the polysilicon film covering the convex portions of the substrate is exposed.   The substrate after polishing is pressed against a cleaning cloth on a surface plate for cleaning, and the substrate and the cleaning cloth are relatively moved while supplying the cleaning liquid between the substrate and the cleaning cloth. A method for cleaning a semiconductor substrate, wherein the abrasive particles adhering to the substrate are cleaned using the semiconductor substrate cleaning liquid according to claim 1.   A semiconductor substrate characterized in that the abrasive particles adhering to the substrate are cleaned using a cleaning brush while supplying the semiconductor substrate cleaning liquid according to any one of claims 1 to 10 to the substrate after polishing. Cleaning method.   The method for cleaning a semiconductor substrate according to claim 11, further comprising a step of removing droplets attached to the substrate after the cleaning.

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