Classifications

• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
  • C09K3/00—Materials not provided for elsewhere
  • C09K3/14—Anti-slip materials; Abrasives
  • C09K3/1454—Abrasive powders, suspensions and pastes for polishing
  • C09K3/1463—Aqueous liquid suspensions
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09G—POLISHING COMPOSITIONS; SKI WAXES
  • C09G1/00—Polishing compositions
  • C09G1/02—Polishing compositions containing abrasives or grinding agents
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
  • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
  • H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
  • H01L21/04—Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer
  • H01L21/18—Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer the devices having semiconductor bodies comprising elements of Group IV of the Periodic Table or AIIIBV compounds with or without impurities, e.g. doping materials
  • H01L21/30—Treatment of semiconductor bodies using processes or apparatus not provided for in groups H01L21/20 - H01L21/26
  • H01L21/31—Treatment of semiconductor bodies using processes or apparatus not provided for in groups H01L21/20 - H01L21/26 to form insulating layers thereon, e.g. for masking or by using photolithographic techniques; After treatment of these layers; Selection of materials for these layers
  • H01L21/3105—After-treatment
  • H01L21/31051—Planarisation of the insulating layers
  • H01L21/31053—Planarisation of the insulating layers involving a dielectric removal step

Definitions

• the present invention relates to a polishing agent based on SiO and a method for producing planar layers.
• Integrated circuits consist of structured semiconducting, non-conducting and electrically conductive thin layers. These structured layers are usually produced by using a layer material, e.g. applied by vapor deposition and by a microlithographic
• Procedure is structured.
• the electronic circuit elements of the IC e.g. Transistors, capacitors, resistors and wiring are generated.
• planarity of the layers decreases significantly with an increasing number of layers. From a certain number of layers, this leads to the failure of one or more functional elements of the IC and thus to the failure of the entire IC.
• the reduction in the planarity of the layers is due to the build-up of new layers when these have to be applied to layers that have already been structured.
• Structuring creates height differences that can be up to 0.6 ⁇ m per layer. These differences in height add up from layer to layer and mean that the subsequent layer no longer has to be applied to a planar surface but to an uneven surface. A first consequence is that the subsequently applied one has an uneven thickness. In extreme cases, this happens
• CMP chemical mechanical polishing
• a CMP step is carried out with the help of special polishing machines, polishing cloths
• a polishing slurry is a composition that, in combination with the polishing cloth, the so-called pad, causes the material to be polished to be removed on the polishing machine.
• CMP slurries have a decisive influence on the polishing behavior during the polishing process. So far, it has been assumed that both chemical and mechanical processes have an influence. For this reason, specific polishing slurries are required for different polishing steps.
• polishing non-conductive layers for example made of silicon dioxide
• polishing electrically conductive layers predominantly metals such as tungsten, aluminum and copper.
• Polishing silicon dioxide is called oxide CMP.
• oxide CMP there are also a number of different polishing steps, which differ in the task of silicon dioxide in the respective layer structure and the number and type of layer materials involved in the layer structure.
• ILD polishing step interlayer dielectric
• STI step shallow trench isolation
• the requirements for the precision of the polishing step and thus for the polishing slurry are particularly high.
• the criteria for evaluating the effectiveness of polishing slurries are a number of variables that are used to characterize the effectiveness of the polishing slurry. This includes the removal rate, i.e. the speed at which the material to be polished is removed, the selectivity, i.e. the ratio of the removal rates of material to be polished to other materials present, as well as sizes for the removal rate.
• the parameters for the uniformity of the planarization are usually the uniformity of the residual layer thickness within a wafer (WIWNU, within-wafer-non uniformity) and the uniformity from wafer to wafer (WTWNU, wafer-to-wafer non uniformity) as well as the number of defects per unit area used.
• a wafer is a polished silicon wafer on which integrated circuits are built.
• polishing slurries based on silicon dioxide have found particular use in practice.
• the raw material for the production of the polishing slurries is usually pyrogenic silica, which consists of large aggregates of smaller primary particles, ie small, mostly spherical primary particles are firmly bonded in pyrogenic silica to form larger, irregularly shaped particles.
• pyrogenic silica which consists of large aggregates of smaller primary particles, ie small, mostly spherical primary particles are firmly bonded in pyrogenic silica to form larger, irregularly shaped particles.
• shear energy for example by intensive stirring, in mixtures of water or alkaline media and pyrogenic silica.
• the aggregates of the fumed silica are crushed by the shear energy.
• the effectiveness of the input of the shear energy depends on the particle size, it is not possible to produce particles of the size and shape of the primary particles by means of the shear forces.
• the polishing slurries produced in this way therefore have the disadvantage that the comminution is not carried out completely and aggregates of primary silica particles remain in the slurry. This coarse particle content can lead to increased formation of scratches and other undesirable defects on the surface to be polished.
• EP-A-899 005 teaches how to avoid the coarse particle fraction by filtration, but this is complex and only partially solves the problem, since aggregates remain below the filtration limit and, because of their non-spherical shape, can further damage the surface to be polished.
• WO 96/027 2096, US-A-5 376 222 and EP-A-520 109 teach the use of basic silica sols with a pH between 9 and 12.5. This pH is adjusted by adding alkali hydroxide or amines.
• polishing slurries have the advantage that they consist practically exclusively of discrete spherical particles, which only to a small extent lead to scratches and other defects on the surface to be polished.
• the disadvantage of these polishing slurries is their lower removal rate.
• basic polishing accelerators in polishing slurries based on silicon dioxide is limited due to the chemical equilibrium for silicon dioxide. Above a certain amount of hydroxide ions, these react with the silicon dioxide particles and dissolve them into silicates (peptization). Therefore, polishing slurries with a pH of over 12 are unstable and difficult to handle in technology.
• EP-A-874 036 and US-A-5 876 490 an attempt is made to solve this problem by providing the silicon dioxide particles with coatings of polymers or cerium dioxide.
• JP 09/324 174 proposes organic polymers and polysiloxanes for this purpose.
• coatings made of aluminum oxide in US-A-4 664 679 surface modifications to reduce the silanol groups on the surface are described.
• polishing slurries based on silicon dioxide particles.
• a certain amount of freely accessible silicon dioxide surface is required to achieve sufficient removal rates.
• these spherical surfaces are required for the deposition of the material removed from the surface to be polished.
• polishing slurries have unsatisfactory polishing rates despite increased amounts of polishing accelerators.
• a surface treatment of the polishing agent particles makes the polishing slurry and thus the polishing slurry more expensive
• This object is surprisingly achieved by providing polishing agents based on silica sols with a bimodal particle size distribution.
• polishing agents now found have improved removal rates and increased selectivities compared to polishing agents of the prior art.
• the invention therefore relates to polishing agents containing spherical, discrete silicon dioxide particles which are not linked to one another by bonds, characterized in that the polishing agent
• the invention also relates to processes for producing planar
• the polishing agents according to the invention do not contain silicon dioxide particles linked to one another via bonds. They have solids contents of 1 to 60% by weight, preferably 1 to 30% by weight, particularly preferably 5 to 20% by weight, it being possible to adjust the desired solids contents by adding water.
• polishing agents according to the invention can also contain other additives such as Contain polishing accelerators, surface-active substances or compounds for viscosity adjustment.
• the polishing agents according to the invention are based on silica sols.
• Silica sols do not contain silicon dioxide particles linked together by bonds.
• Silica sols are sedimentation-stable, colloidal solutions of amorphous SiO in water or alcohols and other polar solvents. They are mostly water-liquid, and the commercial products have e.g. T. high solids concentrations (up to 60 wt .-%) and have great stability against gelation.
• the silica sols are milky cloudy, opalescent to colorless, clear depending on the particle size of the silicon dioxide particles.
• the particles of the silica sol have diameters of 5 nm to 250 nm, preferably 5 nm to 150 nm.
• the particles are spherical, spatially limited and preferably electrically negatively charged. in the
• SiOH groups are often arranged on the surface.
• Stable silica sols with specific surfaces of approximately 30 to 1000 m 2 / g are preferred. The specific surfaces can either be measured using the BET method (see S. Brunauer, PH
• the silica sols usually have a viscosity of less than
• the viscosity of the silica brine depends on the particle size, the content of electrolytes, the silicon dioxide content and the degree of crosslinking of the particles.
• the silica sols used are preferably uncrosslinked and stable against gelation.
• the stability to irreversible gelation to silica gel which is based on a spatial crosslinking with the formation of Si-O-Si bonds between the particles, decreases with increasing silicon dioxide content, increasing electrolyte contamination and decreasing particle size.
• fine-particle silica sols for example those with particle sizes smaller than 6 nm
• coarse-particle silica sols with for example particle sizes greater than 50 nm in which solids contents up to 60 wt .-% can be achieved.
• the pH of the silica sols used is between 1 and 12.
• the pH value of the silica sols used is preferably between 9 and 11.
• the range between pH 5 and pH 6 is less preferred since silica sols have only a low stability in this range.
• peptization and dissolution of the particles then increasingly occur with the formation of alkali silicate solution.
• Silica sols are unstable towards the addition of electrolytes, e.g. Sodium chloride,
• silica sols contain alkali, e.g. Sodium or potassium hydroxide solution, ammonia or other alkalis. Silica sols without addition of electrolyte are therefore preferred.
• Silica sols can be obtained by condensing dilute silicic acid solutions freshly prepared from molecular silicate solutions, less frequently by peptizing silica gels, or by other processes. The majority of the processes carried out on an industrial scale for the production of silica sols use technical water glasses as the starting material. Sodium water glasses or potassium water glasses are suitable for the process, sodium water glasses being preferred for cost reasons. Commercial sodium water glass has a composition of Na 2 O '3.34 SiO 2 and is usually produced by melting quartz sand with soda or a mixture of sodium sulfate and coal, whereby a transparent, colorless glass is obtained, so-called.
• Piece of glass This ground glass reacts in the ground form with water at elevated temperature and pressure to form colloidal, strongly alkaline solutions, which are then subjected to cleaning.
• SiO 2 raw materials can be digested with alkalis directly into aqueous water glasses under hydrothermal conditions.
• De-alkalization is the treatment of dilute water glass solutions with cation exchangers in the H + form.
• Water glass solutions with a silicon dioxide content of less than 10% by weight are preferably passed over exchange columns. Short residence times in the exchange zone, in which the pH of the solutions is 5 to 7, are important in order for the solutions to gel and silicify
• the resulting dilute silicic acid solution (so-called fresh sol) is very unstable and is preferably stabilized and concentrated immediately by renewed alkalization and thermal treatment.
• the silica sol is particularly preferably stabilized by alkalizing the solution to an SiO 2 : Na 2 O ratio of 60 to 130: 1, heating part of the solution to enlarge the particles to 60 to 100 ° C., and then continuously adding fresh sol solution and can grow on the already existing particles. Simultaneously or subsequently, the solution can be concentrated to the desired concentration by evaporation.
• a desired particle size spectrum can be set by precise reaction control, pH control, temperature control or by specifically setting the residence times. It is also possible to add so-called germ brine in addition to the fresh brine.
• Silica sols with defined particle size distributions can be used as the seed brine.
• silica sols used by further processes are also possible. For example, this is possible by hydrolysis of tetraethoxysilane (TEOS). Silica sols obtained by this process have only limited use as polishing agents in semiconductor production because of their high price.
• TEOS tetraethoxysilane
• silica sol A detailed description of the silica sol can be found in K.K. Her, The Chemistry of Silica, Chapter 4, pp. 312-461, Wiley & Sons, New York, 1979.
• silica sols which are produced by dealkalization of water glasses and subsequent stabilization and which have a bimodal particle size distribution.
• the particle sizes of the silica sols used are in a distribution which is 5-95% by weight, preferably 20-80% by weight, of particles in a size distribution of 5-50 nm and the 95-5% by weight, preferably 80 - Contain 20 wt .-% of particles in a size distribution of 50 to 200 nm.
• Bimodal means that there is at least a minimum between two maxima in the particle size distribution.
• the ultracentrifuge is particularly well suited to recognizing bimodal particle size distributions.
• the special feature of the ultracentrifuge is that the dispersion is fractionated according to the particle size before the actual measurement. As is well known, the large particles sediment faster in a homogeneous dispersion than the medium and small particles that are also present.
• the ultracentrifuge cell is irradiated with laser light, a marked change in intensity occurs depending on the time. The change in concentration of the particles and the particle size distribution can be calculated from this change in intensity.
• the light source is a He-Ne laser.
• the ultracentrifuge enables high accuracy, high resolving power, and the distributions can be determined exactly, which is particularly important for bimodal distributions.
• Bimodal silica sols can be produced by mixing monomodal silica sols. Mixtures with different amounts of monomodal silica sols can be set, one silica sol component having a maximum particle size between 5 and 50 nm and the second silica sol component having a maximum particle size between 50 and 200 nm. Bimodal silica sols can optionally also be produced during stabilization. The production of bimodal silica sols by a mixing process is preferred, since the desired quantitative ratios can be set in a significantly more reproducible manner in this process.
• the sol is formulated into a polishing slurry e.g. by dilution with water and the possible addition of additives. Additives can be added in amounts of 0.01% to 10% by weight, based on the polishing slurry.
• the polishing agent silica sols have pH values of preferably 9 to 12, particularly preferably 10 to 11.
• Values can be set, for example, by adding alkali metal hydroxides, such as potassium and sodium hydroxide, amines or ammonia or tetraalkylammonium hydroxides. Also suitable are salts which react alkaline during the hydrolysis, such as sodium carbonate, sodium hydrogen carbonate, potassium carbonate, potassium hydrogen carbonate and ammonium hydrogen carbonate.
• alkali metal hydroxides such as potassium and sodium hydroxide, amines or ammonia or tetraalkylammonium hydroxides.
• salts which react alkaline during the hydrolysis such as sodium carbonate, sodium hydrogen carbonate, potassium carbonate, potassium hydrogen carbonate and ammonium hydrogen carbonate.
• Suitable amines are, for example, primary amines, secondary amines, tertiary amines, heterocyclic amines, tri amines, tetramines or pentamines.
• Tetraalylammonium hydroxides which can be used are, for example, tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide and tetrabutylammonium hydroxide.
• Additional agents can be added to improve the performance of the polishing slurries: e.g. surfactants such as alkyl sulfates, alkyl sulfonates, phenols, glycols or fluorosurfactants or e.g. viscosity-adjusting substances such as polyelectrolytes, polyacrylic acids, polyethylene amines and polysiloxanes.
• surfactants such as alkyl sulfates, alkyl sulfonates, phenols, glycols or fluorosurfactants
• viscosity-adjusting substances such as polyelectrolytes, polyacrylic acids, polyethylene amines and polysiloxanes.
• Surfactants are preferably anionic, cationic or nonionic low molecular weight, oligomeric or polymeric emulsifiers, surfactants or protective colloids.
• anionic low molecular weight, oligomeric or polymeric emulsifiers or surfactants are alkali or alkaline earth metal salts of fatty acids, e.g. Sodium salts of saturated fatty acids with 10 to 21 carbon atoms, sodium salts of unsaturated fatty acids with 12 to 18 carbon atoms, alkyl ether sulfonates such as ethers of sulfo-hydroxy-polyethylene glycols with e.g. 1-methylphenylethyl-phenol, nonylphenol or alkyl ethers with 12 to 18 carbon atoms, aryl-alkyl-sulfonates such as those provided with straight-chain or branched butyl groups
• Naphthalenesulfonic acids or alkyl sulfates such as the sodium salts of long-chain sulfuric acid alkyl esters.
• cationic low molecular weight, oligomeric or polymeric emulsifiers or surfactants are the salts of long-chain alkane radicals containing amines having 8 to 22 carbon atoms, which have been reacted with acids or by alkylation to give the ammonium compounds, and analogous phosphorus and sulfur compounds.
• nonionic oligomeric or polymeric emulsifiers or surfactants examples include
• Alkyl polyglycol ethers or esters such as ethoxylated saturated or unsaturated binary long-chain alcohols containing, for example, 12 to 18 carbon atoms, ethoxylated castor oil, ethoxylated (coconut) fatty acids, ethoxylated soybean oil, ethoxylated resinic or rosinic acids, ethoxylated and optionally propoxylated butyl diglycol, ethoxylated alkyl aryl ethers such as ethoxylated straight-chain phenylphenol and / or branched octylphenol and / or branched benzylated p-hydroxybiphenyl, ethoxylated tri- and diglycerides and alkyl polyglycosides.
• ethoxylated saturated or unsaturated binary long-chain alcohols containing, for example, 12 to 18 carbon atoms
• ethoxylated castor oil ethoxyl
• emulsifiers or surfactants are ethoxylated long-chain alkyl- or alkenylamines, lecithin, reaction products of polyethylene glycols and diisocyanates modified with long-chain alkyl isocyanates, reaction products of rapeseed oil and diethanolamine or ethoxylated reaction products of sorbitan and long-chain alkane or alkenecarboxylic acids.
• So-called protective colloids are also suitable, e.g. Polyvinyl alcohols or water-soluble cellulose derivatives such as methyl cellulose.
• Examples 2 to 4 are shown in the table with the removal rates and selectivities of the silica sols according to the invention and of the comparison silica sols.
• the polishing conditions are summarized below.
• example 2 the results of the polishing test with the polishing slurry with the bimodal silica sol according to the invention from example 1 are given.
• example 3 For the polishing slurry in polishing test 3, a
• Silica sol with an average particle size of 70 nm (Fig.2) was used.
• the polishing slurry in polishing test 4 contains a finely divided silica sol with an average particle size distribution of 15 nm (Fig.l).
• Unstructured (blanket) wafers with a diameter of 200 mm are used.
• the thickness of the oxide layer (TEOS) is 10,000 angstroms and the thickness of the nitride layer is 6,000 angstroms.
• the oxide removal rate (TEOS) is given in angstroms per minute
• Selectivity indicates the ratio of the rate of removal of the oxide to the silicon nitride.

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• Chemical & Material Sciences (AREA)
• Organic Chemistry (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Mechanical Treatment Of Semiconductor (AREA)
• Polishing Bodies And Polishing Tools (AREA)
• Finish Polishing, Edge Sharpening, And Grinding By Specific Grinding Devices (AREA)
• Silicon Compounds (AREA)

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• 2001
  • 2001-03-19 CN CNB018074324A patent/CN1240797C/zh not_active Expired - Fee Related
  • 2001-03-19 IL IL15179401A patent/IL151794A0/xx unknown
  • 2001-03-19 US US10/239,464 patent/US20030061766A1/en not_active Abandoned
  • 2001-03-19 AU AU2001256208A patent/AU2001256208A1/en not_active Abandoned
  • 2001-03-19 AT AT01929438T patent/ATE302830T1/de not_active IP Right Cessation
  • 2001-03-19 WO PCT/EP2001/003113 patent/WO2001074958A2/de not_active Ceased
  • 2001-03-19 JP JP2001572637A patent/JP2003529662A/ja active Pending
  • 2001-03-19 EP EP01929438A patent/EP1274807B1/de not_active Expired - Lifetime
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