Silicon oxide-cerium oxide nuclear shell compounded abrasive granules and preparation thereof and application
Technical field
The invention belongs to the chemical mechanical polishing pulp field in the microelectronics processing, be specifically related to silicon oxide-cerium oxide nuclear shell compounded abrasive granules and preparation thereof and application.
Background technology
Along with the develop rapidly of unicircuit (IC) industry, the IC characteristic dimension is constantly dwindled, and die size constantly increases, and IC technique becomes and becomes increasingly complex with meticulous.At present microelectronics is to being integrated in a future development on the chip with tens components and parts, and this has just caused the three-dimensional of chip structure, the wiring multiple stratification.Yet, realize wiring layer stereo structure at large-diameter silicon wafer, etching technics requires every one deck all should have very high overall planeness, the planeness on layer surface especially, this is the key that realizes multilayer wiring.And traditional glossing can not satisfy this requirement, chemical Mechanical Polishing Technique can not only satisfy this requirement, and can reduce injection defect, can also improve alignment precision by improving surface finish, reduce the purpose that characteristic dimension improves integrated level thereby reach.
The most frequently used polish abrasive is silica abrasive and cerium oxide abrasives in the mechanical polishing of unicircuit chemistry at present.Silica abrasive since its preferably dispersed, homogeneity and cheap price become at present the chemically machinery polished abrasive material of the most extensive employing, and chemical property is more active, rear cleaning process liquid waste disposal is easier to.But its shortcoming is that hardness is slightly low with respect to oxide compound, and clearance is lower, and the clearance between silicon oxide and the silicon nitride is selected lower in the polishing of STI (shallow trench isolation from).Polishing for the silica dioxide medium layer, more external major companies, Cobat such as the U.S., Rodel company, Fujimi Inc. etc. of Japan all adopts large particle diameter abrasive material (about 130nm) to improve mechanical effect in the polishing process, improve polishing speed with this, and then enhance productivity.But this method has also produced the serious problems such as surface tear simultaneously, has been difficult to satisfy the requirement that IC of future generation makes.
Cerium oxide abrasives since its can with silicon oxide generation chemical reaction, so under the same conditions, the polishing speed of cerium oxide approximately is three times of silicon oxide, especially keeps higher clearance in neutral polishing fluid.But it is more expensive that its shortcoming is price, and particle is irregular, not of uniform size, and size-grade distribution is larger, and viscosity is large, reunites easily, can cause scuffing, and its to be deposited on the deielectric-coating absorption serious, for rear cleaning brings difficulty.Consider, cerium oxide abrasives can not satisfy the requirement that IC of future generation makes.
Therefore, how to improve the clearance of silica dioxide medium layer and keep surface quality preferably and how to improve a great problem of the polishing of silicon oxide between silicon nitride in selecting to make than unicircuit.For this reason, many scholars are coated on silicon oxide surface with cerium oxide and form silicon oxide-cerium oxide compounded abrasive, and this compounded abrasive has remedied the shortcoming and defect of single silicon oxide and cerium oxide abrasives.
The people such as Zhenyu Lu are at " Journal of Materials Research " 2003,18 (10): studied the polishing of silicon oxide-cerium oxide compound abrasive to the silicon dioxide layer of thermooxidizing among the 2323-2330, the polishing speed of the silicon oxide that discovery makes-cerium oxide compound abrasive is apparently higher than the pure silica abrasive material.But the preparation method of this abrasive material consists of nucleocapsid structure by the silicon oxide surface that the surface charge of regulating pH value control particle makes its surface potential make on the contrary mutually the cerium oxide of small particle size be adsorbed on large particle diameter, can only use under specific pH value.The people such as Seung-Ho Lee are at " Journal ofMaterials Research " 2003,17 (10): the compounded abrasive of having mentioned silicon oxide surface coating cerium oxide layer among the 2744-2749, and the silicon dioxide layer to thermooxidizing polishes, and the polishing speed of the silicon oxide that discovery makes-cerium oxide compounded abrasive is apparently higher than the pure silica abrasive material.But the silica abrasive of their usefulness all is commodity gaseous oxidation silicon, and particle diameter is 300~400nm, and does not have the application of research in STI.The people such as Xiao Baoqi are at " tribology journal " 2008,28 (2): mentioned the application of silicon oxide-cerium oxide compounded abrasive in optical glass surface processing among the 103-107, but the abrasive material with compounded abrasive and pure zirconia cerium does not compare, and does not demonstrate the advantage of this kind abrasive material.The people such as Chai Mingxia are at " Chinese Journal of Inorganic Chemistry " 2007, (4): 623-629 has also mentioned the silicon oxide-application of cerium oxide compounded abrasive in glass polishing, but the silicon oxide of usefulness makes from organosilicon, cost is higher, and waste reaction solution pollutes more serious, and need in the process of preparation abrasive material may cause the secondary agglomeration of particle through calcining, affect polishing effect.
Summary of the invention
The objective of the invention is to overcome defective of the prior art, a kind of silicon oxide-cerium oxide nuclear shell compounded abrasive granules and preparation thereof and application are provided.
The present invention adopts following technical scheme to solve the problems of the technologies described above:
A kind of silicon oxide-cerium oxide nuclear shell compounded abrasive granules, this silicon oxide-cerium oxide nuclear shell compounded abrasive granules comprises silicon oxide and cerium oxide, and the kernel of described compound abrasive grain is the spherical silica kernel, and shell is the cerium oxide coating layer.
Better, the particle diameter of described compound abrasive grain is 23~160nm; And the particle diameter of described spherical silica kernel is 20~140nm, 50~140nm more preferably, and the particle diameter of described spherical silica kernel is less than the particle diameter of compound abrasive grain.
Better, in the described silicon oxide-cerium oxide nuclear shell compounded abrasive granules, in the gross weight of silicon oxide, the weight percent of cerium oxide is 2~30%, more preferably 2~20%.
The preparation method of silicon oxide-cerium oxide nuclear shell compounded abrasive granules of the present invention comprises the steps:
1) take water glass as raw material, by just pure, crystal seed preparation, increase particle diameter and purification step makes high-purity silicasol;
2) in step 1) in add stablizer in the high-purity silicasol that makes, be heated to 70~100 ℃, add again cerium salt and alkali lye, under 70~100 ℃ temperature condition, react 2~24h, react and carry out ageing after complete, and then through ultrafiltration, dilution, namely make silicon oxide-cerium oxide nuclear shell compounded abrasive head product after the uf processing again;
3) with step 2) in the silicon oxide-cerium oxide nuclear shell compounded abrasive head product that makes carry out carrying out again ultrafiltration, dilution behind the hydrothermal crystallizing, namely making described silicon oxide-cerium oxide nuclear shell compounded abrasive granules after the uf processing again.
Described step 1) in, the preparation method of high-purity silicasol abrasive material can be carried out with reference to prior art by those skilled in the art, and preferred, its preparation process can be carried out with reference to the method described in the Chinese publication CN101077946A.
Better, step 1) in, contain the silicon oxide particle that particle diameter is 20~140nm in the described high-purity silicasol, and in the gross weight of described high-purity silicasol, the weight percent of silicon oxide particle is 2~10%.
Better, step 2) in, described digestion time is 0.5~5 hour, is preferably 2 hours.
Better, step 2) in, described stablizer is polyvinylpyrrolidone (PVP), and with the weighing scale of the silica dioxide granule that contains in the described high-purity silicasol, the weight percent of the stablizer of adding is 0.05~10%, is preferably 0.05~1%.
Better, step 2) in, described cerium salt is selected from cerous salt or tetravalent cerium salt.
Preferably, described cerous salt is selected from cerous nitrate (chemical formula is: Ce (NO
3)
3), (chemical formula is cerous acetate: Ce (CH
3COO)
3), (chemical formula is Cerium II Chloride: CeCl
3) and cerous sulfate (chemical formula is: Ce
2(SO
4)
3) in a kind of.
Preferably, described tetravalent cerium salt is selected from ceric ammonium nitrate (chemical formula is (NH
4)
2Ce (NO
3)
6), (chemical formula is C to the trifluoromethane sulfonic acid cerium
4CeF
12O
12S
4) and ceric sulfate (chemical formula is: Ce (SO
4)
2) in a kind of.
Better, step 2) in, when the cerium salt that adds is cerous salt, also need to when adding cerium salt and alkali lye, add oxygenant; Preferably, described oxygenant is hydrogen peroxide.
Further preferred, with the weighing scale of described high-purity silicasol, the weight percent of the oxygenant of adding is 0.1~5%.
Better, step 2) in, described alkali lye is selected from: the mixture of one or more in potassium hydroxide, urea, vulkacit H and the ammoniacal liquor, more preferably urea.
Better, step 2) in, with the weighing scale of described high-purity silicasol, the weight percent of the cerium salt of adding is 2~20%, the weight percent of the alkali lye of adding is 1~10%.
Better, step 3) in, the temperature of described hydrothermal crystallizing is 100~240 ℃, the time of hydrothermal crystallizing is 1~24 hour.
Described step 2) and step 3) in ultrafiltration step can be determined according to general knowledge known in this field by the technician.
The invention also discloses a kind of polishing fluid for super large-scale integration STI chemically machinery polished, it is characterized in that, contain above-mentioned silicon oxide-cerium oxide nuclear shell compounded abrasive granules in the described polishing fluid.
Better, described polishing fluid for super large-scale integration STI chemically machinery polished also contains pH adjusting agent, tensio-active agent, dispersion agent and water.
Preferably, described polishing fluid for super large-scale integration STI chemically machinery polished, in the gross weight of polishing fluid, the weight percentage ranges of described silicon oxide-cerium oxide nuclear shell compounded abrasive granules is 1~40%.
Further preferred, described polishing fluid for super large-scale integration STI chemically machinery polished, in the gross weight of compounded abrasive, the weight percent of described tensio-active agent is 50~2000ppm, the weight percent of described dispersion agent is 50~5000ppm, and surplus is water.
Better, the pH value of described polishing fluid for super large-scale integration STI chemically machinery polished is 5~12.55, is preferably 9.5~12.55.
Better, described pH adjusting agent is selected from any or its mixture in sulfuric acid, hydrochloric acid, nitric acid, acetic acid, quadrol, hydramine, potassium hydroxide and the ammoniacal liquor, and those skilled in the art can determine the kind of the pH adjusting agent that adds and concrete add-on according to the pH value.
Better, described tensio-active agent is selected from any in nonionogenic tenside, cats product or the anion surfactant.
Better, described dispersion agent is selected from any in polyacrylic acid, polymaleic acid, poly carboxylic acid, polyamine, polyester and the Sodium hexametaphosphate 99.
Described water can be deionized water or distilled water.
The invention also discloses the preparation method of described polishing fluid for super large-scale integration STI chemically machinery polished, comprise the steps: according to composition and ratio, in above-mentioned silicon oxide-cerium oxide nuclear shell compounded abrasive granules, add pH adjusting agent, tensio-active agent, dispersion agent and water, after mixing, can make described polishing fluid for super large-scale integration STI chemically machinery polished.
Silicon oxide-cerium oxide nuclear shell compounded abrasive granules of the present invention and contain this silicon oxide-chemical mechanical polishing liquid of cerium oxide nuclear shell composite particles and can be used for the fields such as chemically machinery polished of glass substrate, super large-scale integration silica dioxide medium layer and STI, and have higher polishing clearance and polishing and select ratio, while also can reduce the surface imperfection after the polishing, and having preferably, industrial utilization is worth.
Silicon oxide surface among the present invention coats cerium oxide layer and finishes by cerous salt and alkali lye and oxygenant or by tetravalent cerium salt and alkali lye.The purpose that adds oxygenant is to realize that trivalent cerium reduces the synthesis temperature of cerium oxide to ceric conversion under the low temperature, is conducive to eliminate or reduce the reunion of cerium oxide.
The silicon oxide-cerium oxide nuclear shell compounded abrasive granules of the present invention's preparation is applied in the chemically machinery polished of silica dioxide medium layer and STI, with respect to single silica abrasive, can improve polishing clearance and the polishing in the STI polishing of silicon-dioxide and select ratio; With respect to single cerium oxide abrasives, can reduce the surface imperfection after the polishing.
The present invention finds through broad research, adopt surface cladding tech, namely coat the cerium oxide layer film at silicon oxide surface and consist of the nucleocapsid compounded abrasive, the chemical mechanical polishing pulp that utilizes this compounded abrasive to make, not only can obtain than the fast polishing speed of single silica abrasive and high selection than and good surface quality, and than single cerium oxide abrasives easy cleaning.
The silicon oxide that the present invention makes-its kernel of cerium oxide compounded abrasive is silica abrasive, and shell is the cerium oxide coating layer.Because the kernel silica abrasive is comparatively cheap, has saved the high deficiency of single cerium oxide cost; Because kernel silica abrasive dispersiveness is higher, can obtain than the higher compounded abrasive of single cerium oxide abrasives dispersiveness; Since kernel be sphere and size all with, can overcome cerium oxide deficiency irregularly shaped and not of uniform size itself; Because it is higher that the polishing speed of shell cerium oxide and polishing are selected, it is low and select than low deficiency to improve the silica abrasive polishing speed.They remedy mutually, can improve polishing speed and improve surface quality.Remedy the existing deficiency of abrasive material in the chemically machinery polished of silica dioxide medium layer and STI.
Description of drawings
Fig. 1 is the XRD figure of the silicon oxide-cerium oxide nuclear shell compounded abrasive granules that makes among pure zirconia cerium, pure silica and the embodiment 1.
Fig. 2 is the TEM figure of the silicon oxide-cerium oxide nuclear shell compounded abrasive granules that makes of embodiment 1, the situation when wherein Fig. 2 a represents not add stablizer, the situation when Fig. 2 b represents to add stablizer.
Fig. 3 after for the 1 prepared polishing fluid polishing of polishing front glass substrate (a), Comparative Examples glass substrate (b) and the AFM on glass substrate (c) surface after the embodiment 1 prepared polishing fluid polishing scheme.
Embodiment
After now specific embodiments of the invention being described in.Following embodiment is only in order to specifying of the present invention, and scope of the present invention do not done any restriction, and any personnel that are familiar with technique can realize easily that modifications and variations include within the present invention and claims scope.
Embodiment 1
The preparation process of high-purity silicasol (wherein containing particle diameter is the abrasive silica particle of 80nm, and in described high-purity silicasol abrasive material, the weight percent of abrasive silica particle is 10%) is as follows:
1) just pure: as water glass to be diluted to the SiO2 weight content not to be higher than 15%, filter, then filtrate is exchanged by resin cation (R.C.), remove sodium ion and other cation impurities;
2) crystal seed preparation: it is 11.0 that the liquid after just pure is adjusted to pH, is heated to gradually 60~135 ℃ under agitation condition, carries out the polymerization of crystal seed, makes the silicon sol of high evenness after the cooling;
3) increase particle diameter: the silicon sol of the high degree of dispersion that seed crystal production process is made is warming up to 60 ~ 135 ℃ under agitation condition, add temperature and be not higher than the pure liquid that obtains at the beginning of 50 ℃, the control feeding quantity be not higher than the silicon sol volume of the high evenness that 4 times of crystal seeds prepare/hour, reinforced flow velocity is 30m/s, obtains the silicon-dioxide coarse abrasive;
4) purifying: the silicon-dioxide coarse abrasive is exchanged through resin cation (R.C.) and resin anion(R.A), obtain the finished product abrasive silica.
Getting 200g is 80nm by the particle diameter that the crystal growth makes, concentration is 10% high-purity silicasol, add 0.2gPVP, then be heated to 100 ℃, adding 200g contains the mixing solutions of the urea of 5.48g ceric ammonium nitrate and 2.40g, reacts complete rear ageing 2 hours, then carries out ultrafiltration, dilute with deionized water after the ultrafiltration, and then can make silicon oxide-cerium oxide compounded abrasive head product after the uf processing; Again this head product is inserted hydrothermal reaction kettle, 200 ℃ of lower crystallization 24 hours, finally making particle diameter was 90nm, is coated with the nucleocapsid compounded abrasive with respect to silicon oxide weight 20% cerium oxide.Characterize with the phase structure of XRD diffractometer to the sample of gained, and with the pattern of the prepared sample of transmission electron microscope observation.
Pressing the compounded abrasive of the processing parameter preparation of embodiment 1 composes more as shown in Figure 1 with the XRD figure of pure silica and pure zirconia cerium, can find out, obvious cerium oxide characteristic diffraction peak has appearred in the XRD figure spectrum of prepared compounded abrasive, and the characteristic diffraction peak of silicon oxide weakens, and may cause owing to cerium oxide particle is coated on silicon oxide surface.In addition, do not add PVP, other step compares with embodiment 1 and interpolation PVP, TEM characterizes as shown in Figure 2, the situation when wherein Fig. 2 a represents not add stablizer, the situation when Fig. 2 b represents to add stablizer, by finding out among Fig. 2, after adding PVP, the cerium oxide coating layer of silicon oxide surface is more complete, evenly.
After the silicon oxide-cerium oxide nuclear shell compounded abrasive granules preparation is finished, with the compound abrasive grain that makes and the polishing fluid that can make after Determination of Polyoxyethylene Non-ionic Surfactants, polyacrylic acid (dispersion agent) and deionized water mix for super large-scale integration STI chemically machinery polished, gross weight in this polishing fluid, the weight percent of compound abrasive grain is 40%, the weight percent of Determination of Polyoxyethylene Non-ionic Surfactants is 50ppm, polyacrylic weight percent is 50ppm, and surplus is deionized water.
Embodiment 2
(wherein contain particle diameter is the abrasive silica particle of 140nm to high-purity silicasol, and in described high-purity silicasol abrasive material, the weight percent of abrasive silica particle is 10%) preparation, the preparation method is with embodiment 1, wherein increase the particle diameter step and repeat, can make the larger high-purity silicasol of particle diameter.
Getting 200g is 140nm by the particle diameter that the crystal growth makes, 10% high-purity silicasol that concentration is, add 0.1gPVP, then be heated to 100 ℃, adding 200g contains the mixing solutions of the urea of 19.12g ceric ammonium nitrate and 8.37g, reacts complete rear ageing 2 hours, then carries out ultrafiltration, dilute with deionized water after the ultrafiltration, and then can make silicon oxide-cerium oxide compounded abrasive head product after the uf processing; Again this head product is inserted hydrothermal reaction kettle, 200 ℃ of lower crystallization 24 hours, finally making particle diameter was 160nm, and the particle diameter of compounded abrasive is coated with the nucleocapsid compounded abrasive with respect to silicon oxide weight 30% cerium oxide.
Comparative Examples 1
The high-purity silicasol that makes among the embodiment 1 directly is used as abrasive material polishes test.
The polishing test
Use respectively the abrasive material of embodiment 1 and Comparative Examples 1, do not add chemical additive, just the pH value is transferred to 10 namely gets polishing fluid, under the following conditions the CD glass substrate is polished test.
Table 1 polishing condition
Polishing machine |
CP-4 (production of CETR company) |
Workpiece |
The soda lime glass substrates of 2inch |
Polishing pad |
LP66 (the global optics production of the U.S.) |
Polish pressure |
5psi |
The rubbing head rotating speed |
100rpm |
The polishing pad rotating speed |
100rpm |
The polishing fluid flow velocity |
100mL/min |
The polishing test result sees Table 2.Can find out that it is many that material removing rate is promoted to original twice, and damaging surface roughness not.
Table 2 polishing test result
Sample |
Material removing rate (nm/min) |
RMS(nm) |
Comparative Examples 1 |
58.49 |
1.024 |
Embodiment |
126.41 |
1.073 |
Adopt the surface appearance feature of AFM Analysis glass substrate.The polishing effect of embodiment 1 and Comparative Examples 1 respectively referring to Fig. 3 (a) and (b).As seen from the figure, the polishing fluid that adopts compounded abrasive of the present invention to make can obtain nearly flawless super-smooth surface.
Embodiment 3
The preparation method of high-purity silicasol (wherein containing particle diameter is the abrasive silica particle of 20nm, and in described high-purity silicasol abrasive material, the weight percent of abrasive silica particle is 2%) is with embodiment 1.
Getting 200g is 20nm by the particle diameter that the crystal growth makes, concentration is 2% high-purity silicasol, add 0.8gPVP, then be heated to 70 ℃, add the mixing solutions that 200g contains the ammoniacal liquor of 0.8g cerous nitrate and 0.8g, then add the hydrogen peroxide of 0.1g, react complete rear ageing 5 hours, then carry out ultrafiltration, dilute with deionized water after the ultrafiltration, and then can make silicon oxide-cerium oxide compounded abrasive head product after the uf processing; Again this head product is inserted hydrothermal reaction kettle, 240 ℃ of lower crystallization 1 hour, finally making particle diameter was 23nm, is coated with the nucleocapsid compound abrasive grain with respect to silicon oxide weight 30% cerium oxide.
After the silicon oxide-cerium oxide nuclear shell compounded abrasive granules preparation is finished, with the compound abrasive grain that makes and the polishing fluid that can make after quaternary cationics, polymaleic acid (dispersion agent) and deionized water mix for super large-scale integration STI chemically machinery polished, gross weight in this polishing fluid, the weight percent of compound abrasive grain is 1%, the weight percent of Determination of Polyoxyethylene Non-ionic Surfactants is 2000ppm, polyacrylic weight percent is 5000ppm, and surplus is deionized water.
Adopt the polishing fluid that makes in the present embodiment to be used for the mechanical polishing of unicircuit silica dioxide medium layer, can obtain nearly flawless super-smooth surface.
Embodiment 4
The preparation method of high-purity silicasol (wherein containing particle diameter is the abrasive silica particle of 140nm, and in described high-purity silicasol abrasive material, the weight percent of abrasive silica particle is 10%) is with embodiment 2.
Getting 200g is 140nm by the particle diameter that the crystal growth makes, concentration is 10% high-purity silicasol, add 2gPVP, then be heated to 90 ℃, add the mixing solutions that 200g contains the ammoniacal liquor of 4g cerous acetate and 2g, then add the 1g hydrogen peroxide, react complete rear ageing 4 hours, then carry out ultrafiltration, dilute with deionized water after the ultrafiltration, and then can make silicon oxide-cerium oxide compounded abrasive head product after the uf processing; Again this head product is inserted hydrothermal reaction kettle, 240 ℃ of lower crystallization 1 hour, finally making particle diameter was 155nm, is coated with the nucleocapsid compound abrasive grain with respect to silicon oxide weight 30% cerium oxide.
After the silicon oxide-cerium oxide nuclear shell compounded abrasive granules preparation is finished, with the compound abrasive grain that makes and the polishing fluid that can make after quaternary cationics, polyacrylic acid (dispersion agent) and deionized water mix for super large-scale integration STI chemically machinery polished, gross weight in this polishing fluid, the weight percent of compound abrasive grain is 1%, the weight percent of Determination of Polyoxyethylene Non-ionic Surfactants is 100ppm, polyacrylic weight percent is 500ppm, and surplus is deionized water.
Adopt the polishing fluid that makes in the present embodiment to be used for the mechanical polishing of unicircuit silica dioxide medium layer, can obtain nearly flawless super-smooth surface.