KR101733164B1 - Slurry and substrate polishing method using the same - Google Patents
Slurry and substrate polishing method using the same Download PDFInfo
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- KR101733164B1 KR101733164B1 KR1020150135380A KR20150135380A KR101733164B1 KR 101733164 B1 KR101733164 B1 KR 101733164B1 KR 1020150135380 A KR1020150135380 A KR 1020150135380A KR 20150135380 A KR20150135380 A KR 20150135380A KR 101733164 B1 KR101733164 B1 KR 101733164B1
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- abrasive
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- tungsten layer
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- 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
- C09K3/1409—Abrasive particles per se
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B24—GRINDING; POLISHING
- B24B—MACHINES, DEVICES, OR PROCESSES FOR GRINDING OR POLISHING; DRESSING OR CONDITIONING OF ABRADING SURFACES; FEEDING OF GRINDING, POLISHING, OR LAPPING AGENTS
- B24B37/00—Lapping machines or devices; Accessories
- B24B37/02—Lapping machines or devices; Accessories designed for working surfaces of revolution
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- 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
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- 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 at least one potential-jump barrier or surface barrier, e.g. PN junction, depletion layer or carrier concentration layer
- H01L21/18—Manufacture or treatment of semiconductor devices or of parts thereof the devices having at least one potential-jump barrier or surface barrier, e.g. PN junction, depletion layer or carrier concentration layer the devices having semiconductor bodies comprising elements of Group IV of the Periodic System 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
- H01L21/302—Treatment of semiconductor bodies using processes or apparatus not provided for in groups H01L21/20 - H01L21/26 to change their surface-physical characteristics or shape, e.g. etching, polishing, cutting
- H01L21/306—Chemical or electrical treatment, e.g. electrolytic etching
- H01L21/30625—With simultaneous mechanical treatment, e.g. mechanico-chemical polishing
Abstract
The present invention relates to a slurry and a substrate polishing method using the slurry.
A slurry according to an embodiment of the present invention is a slurry for tungsten polishing, comprising: an abrasive for performing polishing; A dispersing agent for dispersing the abrasive; And an oxidizing agent for oxidizing the tungsten surface, wherein the abrasive includes first abrasive grains having an average primary particle size of less than 60 nm and second abrasive grains larger than the first abrasive grains.
Such a slurry not only has a high polishing rate for the tungsten layer but also can perform uniform polishing irrespective of the element structure under the tungsten layer.
Description
The present invention relates to a slurry and a substrate polishing method using the slurry, and more particularly, to a slurry capable of uniformly polishing a tungsten layer by a chemical mechanical polishing process in a semiconductor manufacturing process and a substrate polishing method using the slurry.
A chemical mechanical polishing (CMP) process refers to a process of polishing an object by providing a slurry containing an abrasive and various compounds while rotating the surface of the substrate such as a semiconductor wafer by contacting the polishing pad. That is, the surface of the substrate or its upper layer is chemically and mechanically polished by the slurry and the polishing pad to be planarized. Generally, it is known that the metal polishing process is repeatedly performed in a process in which a metal oxide (MO x ) is formed by an oxidizing agent and a process in which a metal oxide formed is removed by an abrasive. The polishing process of the tungsten layer, which is widely used as the wiring of various semiconductor devices, also proceeds by a mechanism in which tungsten oxide (WO 3 ) is formed by an oxidizing agent and tungsten oxide is removed by an abrasive.
On the other hand, the size of the semiconductor device is gradually reduced and the number of metal wiring layers is increased, and the shapes and densities of the patterns formed according to the respective regions in the device are different. Accordingly. Irregularities on the surface or in each region in each layer are then transferred to the upper layer, making it more difficult to uniformly polish the upper layer. For example, a tungsten layer with various patterns at the bottom is very difficult to uniformly polish.
In order to improve the polishing performance of the tungsten layer, various components are added to the slurry or the content of the oxidizing agent and the catalyst contained in the slurry is controlled. Despite these efforts, however, slurries have not yet been developed that are capable of polishing the tungsten layer uniformly with excellent polishing rates.
Meanwhile, Korean Patent Publication No. 10-1409899 discloses a polishing slurry for controlling the potential of an abrasive. In this case, however, it is not possible to uniformly polish a tungsten layer having irregularity in each region.
The present invention provides a slurry for tungsten polishing and a method for polishing a substrate using the same.
The present invention provides a slurry capable of uniformly polishing a tungsten layer formed on a substrate, and a substrate polishing method using the slurry.
A slurry according to an embodiment of the present invention is a slurry for tungsten polishing, comprising: an abrasive for polishing; A dispersing agent for dispersing the abrasive; And an oxidizing agent for oxidizing the tungsten surface, wherein the abrasive includes first abrasive grains having an average primary particle size of less than 60 nm and second abrasive grains larger than the first abrasive grains.
The abrasive may include zirconium oxide particles and may be included in the range of 0.1 wt% to 10 wt% with respect to the total weight of the slurry. The entire first abrasive grains may be smaller than the average primary grain size of the second abrasive grains. The difference between the average primary particle size of the first abrasive particles and the average primary particle size of the second abrasive particles may range from 90 to 130 nm. The difference between the primary particle maximum size of the first abrasive particle and the primary particle minimum size of the second abrasive particle may range from 60 to 100 nm.
The average primary particle size of the first abrasive grains may range from 15 nm to 55 nm, and the average primary particle size of the second abrasive grains may range from 120 nm to 230 nm. The average primary particle size of the first abrasive particles may range from 20 nm to 50 nm and the average primary particle size of the second abrasive particles may range from 130 nm to 180 nm.
The abrasive may contain an amount of the first abrasive grains larger than an amount of the second abrasive grains. In this case, when the total amount of the abrasive is 100, the amount of the second abrasive grains may range from 5 to 50 with respect to the total abrasive. When the total amount of the abrasive is 100, the amount of the second abrasive grains may range from 15 to 25 with respect to the whole abrasive.
According to an embodiment of the present invention, there is provided a substrate polishing method comprising: preparing a substrate on which a tungsten layer is formed; Preparing a slurry including first abrasive grains having an average size of primary particles of less than 60 nm and second abrasive grains having an average size of primary grains larger than that of the first abrasive grains; And polishing the tungsten layer while supplying the slurry onto the substrate.
The step of forming the substrate on which the tungsten layer is formed includes the steps of forming a first region where a plurality of first patterns are formed on a substrate and a second region that is a region other than the first region; And forming a tungsten layer in the first region and the second region.
Wherein the second region has a second pattern different from the first pattern and the density of the first pattern may be higher than the density of the second pattern and the polishing process is performed on the first region and the tungsten And polishing the layers together. The tungsten layer of the second region may be at least one of a grain size and a layer thickness larger than the tungsten layer of the first region, and the polishing process may further comprise a step of forming the tungsten layer of the first region and the tungsten layer of the second region together Polishing process. Here, the abrasive may include zirconium oxide particles and may be contained in an amount ranging from 0.1 wt% to 10 wt% with respect to the total weight of the slurry.
On the other hand, the substrate polishing method may further include a step of subsequently polishing the tungsten layer while supplying a slurry containing only the first abrasive grains with an abrasive. In this case, when the thickness of the entire tungsten layer polished by the polishing process and the subsequent polishing process is 100, the tungsten layer of 70 to 95 is polished by the polishing process, and 5 to 30 tungsten layers are polished by the subsequent polishing process. Polishing can be performed.
According to the embodiment of the present invention, since tungsten is polished by using a slurry including abrasive grains having a small grain size and abrasive grains having a large grain size, it is possible to have a high polishing rate for a tungsten layer, Uniform polishing can be performed irrespective of the device structure. Further, even if the tungsten layer exists in different film quality or thickness depending on the region, the tungsten layer can be uniformly polished.
For example, even if the pattern density or height is different depending on the region in the manufacturing process of the semiconductor device, the tungsten layer formed thereon can finally be polished uniformly and evenly.
Further, according to the embodiment of the present invention, it is possible to reduce the occurrence of scratches while maintaining the polishing rate at the time of polishing the tungsten layer. In particular, scratches can be reduced even though the surface having a large curvature is quickly polished.
Further, according to the embodiment of the present invention, since the polishing is performed quickly and smoothly irrespective of the substructure and the state of the layer to be polished, the subsequent process can be facilitated, and the quality and reliability of the manufactured device can be improved.
1 is a conceptual diagram for explaining the distribution of abrasive grains in the embodiment of the present invention.
2 is an electron micrograph and a size distribution diagram of the first abrasive grain of the present invention.
3 is an electron micrograph and a size distribution diagram of a second abrasive grain of an embodiment of the present invention.
4 is a graph showing polishing characteristics of a slurry in which the content of abrasive grains is changed in the embodiment of the present invention.
5 is a graph showing the polishing rate of the slurry in which the abrasive particle content is changed in the embodiment of the present invention.
6 is a conceptual view for explaining a state of an object to be polished;
Figure 7 is an electron micrograph of a tungsten layer in the first region of Figure 6;
Figure 8 is an electron micrograph of a tungsten layer in the second region of Figure 6;
9 is a conceptual view for explaining the polishing process of the prior art.
10 is a conceptual diagram for explaining a polishing process according to an embodiment of the present invention;
11 is a conceptual diagram for explaining a polishing process according to a modification of the present invention;
Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. It should be understood, however, that the invention is not limited to the disclosed embodiments, but is capable of other various forms of implementation, and that these embodiments are provided so that this disclosure will be thorough and complete, It is provided to let you know completely. The drawings may be exaggerated or enlarged to facilitate understanding of the invention, wherein like reference numerals refer to like elements throughout.
A slurry according to an embodiment of the present invention is a slurry for tungsten polishing, comprising: an abrasive for performing polishing; A dispersing agent for dispersing the abrasive; And an oxidizing agent for oxidizing the tungsten surface, wherein the abrasive comprises a first abrasive particle having an average primary particle size of less than 60 nm and a second abrasive particle larger than the first abrasive particle. In addition, the slurry may include a catalyst for promoting oxide formation, and may further include a disposition regulating agent for controlling the zeta potential of the abrasive. Further, as needed, a polishing selectivity non-adjusting agent for controlling the polishing rate of the objects to be polished, a stabilizer for inhibiting the polishing of substances other than the object to be polished, a corrosion inhibitor for suppressing partial corrosion of the surface of the object to be polished (e.g., tungsten) May be included. Further, a pH adjuster may be further included to adjust the pH of the slurry. In addition, various chemicals may be added depending on the desired performance.
The abrasives, dispersants, oxidants, catalysts and other additives may be contained in the solution. For example, abrasives, dispersants, oxidants, catalysts, and the like are dispersed and distributed in water, particularly DI water. Such a slurry is in the form of an abrasive dispersed in a liquid, and the content of each component is appropriately controlled. On the other hand, the oxidizing agent is not included in the slurry but may be prepared separately from the slurry and added to the slurry immediately before the polishing process.
The abrasive may include abrasive particles having a positive (+) zeta potential. For example, the abrasive particles may comprise zirconium oxide, that is, zirconia (ZrO 2 ) particles. The zirconia particles are in a crystalline phase and have a polyhedral shape with a crystal face. Since zirconia abrasive grains are used as abrasive, mechanical polishing can be dominant in the chemical mechanical polishing process. Therefore, the occurrence of dishing can be suppressed or prevented. In the case of colloidal silica mainly used as a conventional abrasive, it is distributed in a size of about 40 nm to 70 nm, and the average size is about 38.5 nm. The zirconia particles used in the embodiment of the present invention is a crystalline phase of a monoclinic structure and has a polyhedral shape with a crystal face. Further, the abrasive includes first abrasive grains and second abrasive grains having different sizes of the same material.
FIG. 1 is a conceptual diagram for explaining the distribution of abrasive grains in the embodiment of the present invention. FIG. 2 is an electron microscope photograph and a size distribution diagram of the first abrasive grains in the embodiment of the present invention. Microscope photograph and size distribution diagram.
As shown in Fig. 1, the average primary particle size of the first abrasive particles (A) is less than 60 nm, and the average primary particle size of the second abrasive particles (B) is larger than that of the first abrasive particles. Further, the entire first abrasive grains may be smaller than the primary grain average size of the second abrasive grains, and the entire first abrasive grains may be smaller than the primary grain minimum size of the second abrasive grains. That is, the abrasive includes two primary particles whose size is about 3 to 11 times different. Here, the primary particles mean initial particles that do not aggregate with each other. As shown in Fig. 1, these two particles (the first abrasive grains and the second abrasive grains) can be distributed separately from each other in a size that does not overlap, and they can be distributed with a predetermined range. The size difference between these particles (A, b) can be appropriately adjusted. For example, the difference (? D1) between the average primary particle size of the first abrasive particles and the average primary particle size of the second abrasive particles can range from 90 to 130 nm. The difference (? D2) between the maximum primary particle size of the first abrasive particles and the minimum primary particle size of the second abrasive particles can range from 60 to 100 nm. By using two abrasive grains having different sizes as described above, the object can be uniformly polished irrespective of the state of the object to be polished. For example, even when the object to be polished has a region with a large grain size and a large degree of curvature and a region with a small grain size and a small curvature, the object can be uniformly polished by using the polishing slurry of the embodiment. That is, the second abrasive grains having a large size can efficiently polish a region having a large grain size and a large degree of bending, and the first abrasive grains having a small size can efficiently polish a region having a small grain size and a small bend. This will be described in more detail later.
These two particles all range in size from a few tens to several hundreds of nanometers, but the first particle can have a size in the range of several tens of nanometers, and the second particle can have a range of a few hundred nanometers in size. For example, the average primary particle size of the first abrasive particles may range from 15 nm to 55 nm, and the average primary particle size of the second abrasive particles may range from 120 nm to 230 nm. The average primary particle size of the first abrasive particles may range from 20 nm to 50 nm and the average primary particle size of the second abrasive particles may range from 130 nm to 180 nm. If the size of the first abrasive grains is too small, the abrasion rate can be reduced, and if the size of the second abrasive grains is too large, the occurrence of scratches during polishing can be increased. Also, abrasive particles can be uniformly and stably dispersed in the slurry in the above-mentioned particle size range.
The abrasive can precisely control the desired content. First, the abrasive containing the first and second abrasive grains, that is, the whole abrasive agent may be contained in the range of 0.1 wt% to 10 wt% with respect to the total weight of the slurry. If the content of the abrasive is less than 0.1% by weight, the polishing rate is too small to polish or sufficiently abrade the tungsten. On the other hand, when the content of the abrasive is more than 10% by weight, there arises a problem in the dispersion stability of the abrasive particles and the size of the secondary particles becomes excessively large and scratches may occur. In particular, the zirconia particles may be contained in an amount of 0.4 to 2% by weight based on the total weight of the slurry. This is because the tungsten polishing rate is more excellent in the range of 0.4 wt% to 2 wt% and the dispersion stability is sufficiently secured.
Further, the content of the first abrasive grains and the second abrasive grains in the abrasive can be controlled precisely. The abrasive may contain a larger amount of the first abrasive grains than an amount of the second abrasive grains. For example, when the amount of the abrasive is 100, the amount of the second abrasive particles may range from 5 to 50 for the entire abrasive. When the total amount of the abrasive is 100, the amount of the second abrasive particles with respect to the total abrasive may be in the range of 15 to 25. If the amount of the second abrasive grains is too large with respect to the entire abrasive, the abrasion can be roughly performed to quickly remove the large grains and the curvature, but the scratch occurrence probability can be rapidly increased. On the other hand, if the amount of the second abrasive grains is too small, it is very difficult to efficiently and quickly remove the rough surface of the object to be polished.
The dispersant serves to uniformly disperse the abrasive in the slurry, and cationic, anionic and nonionic polymeric materials can be used. Further, the dispersing agent can control the zeta potential of the abrasive. That is, the cationic dispersant can increase the zeta potential of the abrasive agent to positive, that is, the positive potential, and the anionic dispersant can reduce the zeta potential of the abrasive agent to negative, that is, negative potential. In addition, the nonionic dispersant can maintain the zeta potential of the abrasive as it is. Therefore, the zeta potential of the abrasive can be maintained as it is, or finely adjusted to the positive or negative potential depending on the dispersant contained in the slurry.
Examples of the cationic polymer dispersing agent include polylysine, polyethyleneimine, benzethonium chloride, Bronidox, Cetrimonium bromide, Dimethyldioctadecylammoniumchloride, ), Tetramethylammonium hydroxide, distearyl dimethyl ammonium chloride, polydimethylamine-co-epichlorohydrin, 1,2-dioloyoyl- 1,2-dioleoyl-3-trimethylammonium propane, and polyallyl amine. The term " polyamine "
Examples of the anionic polymer dispersing agent include polyacrylic acid, polycarboxylic acid, sodium dodecyl benzene sulfonate, sodium dodecyl sulfate, sodium polystyrene sulfonate (Sodium polystyrene sulfonate).
Examples of the non-ionizing dispersant include polyvinyl pyrrolidone, polyethylene oxide, polyvinyl alcohol, hydroxyethyl cellulose, 2-amino-2-methyl 2-methyl-1-propanol, and beta-cyclodextrin.
The dispersant may be contained in the range of 0.01 wt% to 5 wt% with respect to the total weight of the slurry. If the content of the dispersing agent is less than 0.01% by weight, the dispersion may not be performed well and precipitation may occur. If the content of the dispersing agent exceeds 5% by weight, there is a fear that the dispersion stability of the slurry is lowered due to aggregation of the polymer substance and high ionization concentration . The dispersing agent may be contained in an amount of 0.15 wt% to 1 wt% based on the total weight of the slurry. This is because the dispersion stability is excellent and it is more advantageous to finely control the zeta potential of the abrasive.
The oxidizing agent oxidizes the surface of the object to be polished, for example, tungsten. That is, the oxidizing agent oxidizes the object to be polished, which is a metal, to form a metal oxide film having a weaker strength than the metal. For example, the oxidizing agent oxidizes tungsten to a tungsten oxide film that is weaker in strength than tungsten, facilitating polishing of tungsten. These oxidants include hydrogen peroxide (H 2 O 2 ), urea hydrogen peroxide, ammonium persulfate, ammonium thiosulfate, sodium hypochlorite, sodium periodate At least one selected from the group consisting of sodium periodate, sodium persulfate, potassium iodate, potassium perchlorate, and potassium persulfate. In the embodiment of the present invention, hydrogen peroxide is mainly used.
The content of the oxidizing agent may be in the range of 0.5 wt% to 10 wt% of the total weight of the slurry. When the content of the oxidizing agent is less than 0.5% by weight, oxides are not formed well on the surface of tungsten, so that the polishing rate is low and difficult to polish. When the content of the oxidizing agent exceeds 10% by weight, the reaction with the catalyst becomes violent and the temperature of the slurry increases. Problems may be caused, and the dispersion stability and the polishing efficiency may be lowered by the decomposition reaction of the abrasive. Here, when the content of the oxidizing agent is in the range of 1 wt% to 5 wt%, a high polishing rate and stability of the slurry can be secured. On the other hand, the oxidizing agent may be included in the slurry preparation, may be provided separately from the slurry, may be added to the slurry immediately before the substrate polishing process, mixed and then supplied to the substrate polishing process.
The catalyst accelerates the oxidation of the object to be polished, for example, tungsten. That is, by using a catalyst, the surface oxidation of tungsten can be promoted, and the polishing rate can be increased accordingly. The catalyst causes a reaction known as an oxidant and a Fenton reaction. The Fenton reaction generates OH radicals, which are strong oxidants, and promotes surface oxidation of tungsten. From this, the formation of the tungsten oxide film is promoted and the polishing rate of tungsten is increased. As the catalyst, a compound containing iron may be used. For example, the catalyst may be selected from the group consisting of ammonium iron (III) sulfate, potassium oxalate (K 3 Fe (C 2 O 3 ) 3 ), potassium ferric oxide (Fe-Na), potassium ferricyanide, iron (III) acetylacetonate, ammonium iron (III) citrate, ammonium iron (III) oxalate, Iron (III) chloride, iron (III) nitride, and the like.
The catalyst may be included in an amount of 0.001 wt% to 10 wt% based on the total weight of the slurry. When the catalyst content is less than 0.001 wt%, the polishing rate is too small to polish, and when the catalyst content exceeds 10 wt%, the slurry is discolored and the temperature of the slurry may increase due to the reaction with the oxidizing agent. In addition, the content of the catalyst may be in the range of 0.01 wt% to 5 wt% with respect to the total weight of the slurry. In this case, a stable slurry can be obtained while raising the polishing rate.
The dislocation modifier promotes the oxidation of the tungsten surface and regulates the zeta potential of the abrasive. Although tungsten can be polished without using a dislocation adjusting agent, its polishing rate is very low. That is, by using the dislocation adjusting agent, the surface oxidation of tungsten can be promoted, and the polishing rate can be increased accordingly. In addition, the dislocation adjuster induces anions to control the zeta potential (potential) of the abrasive having a positive dislocation. That is, the potential adjuster can adjust the zeta potential of the abrasive having positive potential to have negative potential. When the zeta potential of the abrasive is adjusted to have negative potential, the residual particles generated by the combination of tungsten and the abrasive after polishing can be minimized and the generation of scratches can be suppressed. For this purpose, the zeta potential of the abrasive can be adjusted to -5 mV to -15 mV. The transition regulator can also control the zeta potential of the abrasive to about -10 mV.
For example, an anionic type polymer material can be used to easily change the zeta potential of the abrasive material in the negative direction. These materials include, but are not limited to, polyacrylic acid, polycarboxylic acid, sodium dodecyl benzene sulfonate, sodium dodecyl sulfate, sodium polystyrene (Sodium dodecyl sulphonate) sulfonate, polystyrene sulfonate, and the like.
The content of the disposing agent may be 0.01 wt% to 1 wt% based on the total weight of the slurry. If the content of the disposing agent is less than 0.01% by weight, the zeta potential of the abrasive agent can not be sufficiently controlled to a negative value, so that the residual particles having the tungsten particles bonded with the abrasive particles can be adsorbed on the surface of tungsten. %, The dispersion stability and the polishing efficiency may be deteriorated rather by the aggregation of the polymer substance. In addition, the disposing agent may be contained in an amount of 0.01% by weight to 0.1% by weight because it is more advantageous to maintain the formation of residual particles and the stability of dispersion.
The stabilizer has a function of suppressing polishing of materials other than the object to be polished. That is, when tungsten is polished, it plays a role of suppressing the polishing of an insulating film, for example, a silicon oxide film, which is a material other than tungsten. As such stabilizer, organic acid may be mainly used. Such materials include, but are not limited to, acetic acid, maleic acid, succinic acid, citric acid, malic acid, oxalic acid, ethylenediaminetetraacetic acid, And malonic acid. ≪ Desc / Clms Page number 7 >
The content of the stabilizer may be 0.01 wt% to 5 wt% based on the total weight of the slurry. When the content of the stabilizer is less than 0.01 wt%, the polishing of the silicon oxide film can not be sufficiently suppressed. If the content of the stabilizer exceeds 5 wt%, the polishing efficiency of the silicon oxide film is lowered and the polishing efficiency of tungsten is also lowered . In addition, the stabilizer may be contained in an amount of 0.1 to 0.2% by weight.
The corrosion inhibitor can inhibit local corrosion which may be caused on the surface of the object to be polished, for example, tungsten. That is, during polishing, pits that are caused by partial corrosion of the tungsten surface can occur, and the corrosion inhibitor can suppress or prevent the corrosion. As a corrosion inhibitor, a polymer series may be mainly used. For example, the corrosion inhibitor may be selected from the group consisting of polyacrylamide, polymethacrylamide, polyalkyleneimine, amino alcohol, ethylenediamine (EDA), diethylene triamine Amines (diethylenetriamine; DETA) and polyethyleneimine (polyethyleneimine).
The corrosion inhibitor may be included in an amount of 0.001 wt% to 0.5 wt% based on the total weight of the slurry. If the content of the corrosion inhibitor is less than 0.001% by weight, the surface of the tungsten is not sufficiently protected and partial corrosion may occur. If the content of the corrosion inhibitor exceeds 0.5% by weight, dispersion stability and polishing efficiency are lowered . The corrosion inhibitor may be included in an amount of 0.0025 wt% to 0.01 wt% based on the total weight of the slurry.
The pH adjusting agent can adjust the pH of the slurry. The pH adjusting agent may mainly include nitric acid, ammonia water and the like. In the embodiment of the present invention, the pH of the slurry can be adjusted to a range of 2 to 4 using a pH adjusting agent. When the potential is positive (+) and the pH is more than 4, the tungsten surface is ionized to form WO 4 2- , and when polishing in this region, the tungsten surface is corroded. On the other hand, when the dislocation is positive (+) and the pH is below 4, soft tungsten oxide (WO 2 , WO 3 ) is formed on the surface of the tungsten surface. Therefore, the slurry of the present invention can easily polish or etch tungsten by adjusting the pH to 4 or less by using a pH adjusting agent such as nitric acid and adjusting the dislocation.
The polishing method of the slurry for tungsten polishing according to the embodiment of the present invention will be described. As the size of the abrasive grains increases, a tungsten layer having a large grain size or a large bend can be quickly removed. In this case, the abrasion proceeds roughly by the large abrasive grain, and the scratch occurrence probability also increases. When the size of the abrasive grains is small, a tungsten layer having a small grain size or a small curvature and a flat surface can be finely polished to a fine portion. However, when such fine abrasive grains are used, it takes a very long time to grind a tungsten layer having a large grain size or a large bending. On the other hand, in the case where the tungsten layer to be polished has different film quality, surface condition, thickness, etc. in each region, it is difficult to uniformly polish the entire tungsten layer even if any abrasive grain is used. However, since the slurry of the embodiment uses an abrasive containing two abrasive grains, the entire tungsten layer can be uniformly polished irrespective of the film quality, surface state, and thickness difference of tungsten. That is, the second abrasive grains having a large size can quickly remove and polish the regions having large grains and a large bend, and the first abrasive grains having a small size can be obtained by using a region having a small grain size and a small curvature, Can be finely polished. Further, since the two abrasive grains are used together, the large particles (second abrasive grains) and the fine grains (first abrasive grains) are simultaneously supplied to the tungsten layer, so that large bending can be removed and fine polishing can proceed, Time may be shortened.
In the following, the results of evaluating the polishing characteristics by preparing the slurry of the above embodiment and applying it to a semiconductor substrate will be described.
[Experimental Example]
The manufacturing process of the slurry is not greatly different from the manufacturing process of the general slurry, and therefore, will be briefly described. First, a vessel to prepare slurry is prepared, and a desired amount of DI water and polyacrylic acid as a dispersing agent are added to the vessel and sufficiently mixed. Two kinds of zirconia particles having a crystalline phase as an abrasive and having an average size of predetermined primary particles were each measured in a desired amount and put into a vessel to be uniformly mixed. In addition, a predetermined amount of anionic polymer material was added as a disposing agent, and a predetermined amount of a catalyst agent was added to the vessel, followed by uniform mixing. In addition, a predetermined amount of citric acid as a stabilizer was poured into a container, and a predetermined amount of polyacrylamide was added thereto as a corrosion inhibitor, followed by uniform mixing. Then, the pH was adjusted by adding a pH adjusting agent such as nitric acid to the container. Hydrogen peroxide water as an oxidizing agent was added to the vessel just before polishing and uniformly mixed to prepare a tungsten slurry. The order of addition and mixing of each of these materials is not particularly limited.
In this Experimental Example, the zirconia particles were added so that the zirconia particles were contained in an amount of 2% by weight based on the total weight of the slurry, and the disposing agent was added in an amount of 0.05% by weight. The dispersant was added so as to contain 0.75 wt%, and the catalyst was added so as to contain 0.03 wt% with respect to the total weight of the slurry, and the oxidant was added so as to contain 1.5 wt%. The stabilizer was added so as to contain 0.1 wt%, and the corrosion inhibitor was added so as to contain 0.005 wt%. At this time, two kinds of zirconia particles were used. The first abrasive grains had an average primary particle size of 35 nm, and the second abrasive grains had an average primary particle size of 150 nm. When the total amount of the zirconia particles was 100%, the contents of the first abrasive grains (A) and the second abrasive grains (B) were changed. That is, the second abrasive grains were changed from 0% to 50% by using the second abrasive grains, and a slurry was prepared. Each slurry was adjusted to have a pH of 2 to 4 using nitric acid. Other than the above components, the remainder may include inevitably impurities and pure water.
Using each of the slurries thus prepared, the tungsten layer deposited on the silicon wafer was polished and the polishing characteristics were observed. In other words, a tungsten film was deposited on the wafer by chemical vapor deposition (CVD). At this time, the deposited tungsten layer was about 250 nm thick on the flat surface and about 100 nm thick on the patterned surface. The tungsten layer was polished using a CMP apparatus. The head and table rotation speed of the apparatus was about 70 rpm, the head pressure was 6 psi, and the flow rate of the slurry supplied was 100 ml / min. While performing the polishing process, the amount (thickness) of the remaining tungsten layer was measured at intervals of about 10 seconds.
Fig. 4 is a graph showing the polishing characteristics of the slurry in which the content of abrasive grains is changed in the embodiment of the present invention, and Fig. 5 is a graph showing the polishing rate of the slurry in which the abrasive grains content is changed in the embodiment of the present invention. Here, the polishing rate of tungsten is calculated by polishing the tungsten layer and measuring the polishing thickness with time, and the thickness of the remaining tungsten is the thickness remaining after polishing the tungsten layer.
4 and 5, in the case where large particles (second abrasive particles) are not used, the abrasion is hardly performed at the beginning, and the abrasion progresses for a certain period of time (about 80 seconds or more) The polishing rate is also increased. On the other hand, it can be seen that the slurry to which the second abrasive grains are added has a faster polishing start time and a higher polishing rate. In addition, when the amount of the second abrasive grain added is increased, the polishing start time (within about 20 seconds) is faster and the polishing rate is also increased. However, if the amount of the second abrasive grain is increased too much, scratches are found to be found on the polished surface. Thus, abrasive grains having different particle sizes can be appropriately used, and the tungsten layer can be polished quickly and uniformly.
Hereinafter, a method of polishing a substrate using a slurry according to an embodiment of the present invention will be described. First, an object to be polished will be described. FIG. 6 is a conceptual view for explaining the state of the object to be polished, FIG. 7 is an electron micrograph of the tungsten layer in the first region of FIG. 6, and FIG. 8 is an electron micrograph of the tungsten layer in the second region of FIG.
The object to be polished includes a first region having a plurality of fine patterns (first patterns) formed on a substrate and having a high pattern density, and a second region having a pattern (second pattern) density lower than that of the first region. For example, a silicon oxide film and a silicon nitride film (second pattern) are formed on a first region having a plurality of trenches (first patterns) in which a silicon oxide film is formed and a silicon nitride film is formed on the semiconductor substrate A second region is provided. The first region and the second region may have a height difference. That is, a step may be generated between two regions. A tungsten layer (W) is formed on the first region and the second region. At this time, the thickness of the tungsten layer of the second region is thicker than that of the first region. For example, the thickness of the tungsten layer in the first region is on the order of 93 nm, and the thickness of the tungsten layer in the second region is on the order of 115 nm on average. 7 and 8, the crystal grains of the tungsten layer in the first region are smaller than the crystal grains of the tungsten layer in the second region. For example, the average grain size of the tungsten layer in the first region is about 113 nm, and the grain size of the tungsten layer in the second region is about 136 nm on average. As described above, the tungsten layer to be polished differs in at least one of the pattern density, the thickness of the layer, and the crystal grain of the layer formed at the bottom of each region. That is, at least one of the pattern density, the thickness of the layer and the crystal grains of the layer is larger or smaller than the other regions. This makes uniform polishing of the entire tungsten layer difficult.
9 is a conceptual diagram for explaining the polishing process of the prior art. In the case of polishing a non-uniform object to be polished by a conventional slurry, uniform polishing is very difficult. As shown in Fig. 9, when a slurry of conventionally used abrasive grains (for example, 40 nm to 70 nm primary particle size) is used to abrade the abrasive article of Fig. 8, the abrasive grains are abraded The polishing of the second region is hardly achieved at the initial stage. In addition, when the tenten layer is polished in a full-scale after a certain amount of bending is removed after a lapse of time, the first region has already been polished so much that its thickness becomes thinner. As a result, the difference in the polishing rate between the two regions is large, so that one side is not polished properly, and the other side is excessively polished, resulting in a thickness difference in each region after polishing, and the thickness or shape of the polished surface becomes uneven.
On the other hand, when the slurry of this embodiment is used, the object to be polished of FIG. 8 can be uniformly polished. 10 is a conceptual diagram for explaining a polishing process according to an embodiment of the present invention.
The polishing method of this embodiment is a method of polishing a substrate, comprising the steps of: providing a substrate on which a tungsten layer is formed; Preparing a slurry including first abrasive grains having an average size of primary particles of less than 60 nm and second abrasive grains having an average size of primary grains larger than that of the first abrasive grains; And polishing the tungsten layer while supplying the slurry onto the substrate. At this time, the object to be polished may include a tungsten layer having a region (a first region and a second region) in the state, and may be the object illustrated in Fig. In addition, the polishing process may include polishing the tungsten layers of the first and second regions together. That is, as shown in Fig. 10, the first and second abrasive grains are supplied together on the tungsten layer, so that the two abrasive grains simultaneously polish the tungsten layer. At this time, the second abrasive grain having a large size rapidly removes the protruding portion of the second region having a large crystal grain and the bending, and the first abrasive grain, which is the fine grain, polishes the fine portion. In addition, the first region has a small grain size and a small curvature on the surface, and the first abrasive grain predominantly acts from the beginning. As described above, the two slurries of the Example work simultaneously on the tungsten layer to polish the first and second regions, so that the entire tungsten layer can be uniformly polished, and each region after polishing has a flat surface with almost no difference in thickness (Fig. 10 (b)). When the slurry of the embodiment is used, the entire tungsten layer can be uniformly polished through a single polishing process using a single slurry.
On the other hand, the substrate polishing method may further include a subsequent polishing process. 11 is a conceptual diagram for explaining a polishing process according to a modification of the present invention. As shown in Fig. 11, the polishing method of the modification may further include a step of polishing the tungsten layer, while supplying a slurry containing only the first abrasive grains with an abrasive. That is, the slurry containing the two particles is used to perform main polishing until the thickness of the tungsten layer is remained to some extent (FIG. 11 (a)), and then the slurry containing only the first abrasive grains is used The tungsten layer is subsequently polished (Fig. 11 (b)). Here, the main polishing process and the subsequent polishing process are performed by polishing the tungsten layer of 70 to 95 by the main polishing process and polishing the tungsten layer of 5 to 30 by the subsequent polishing process, when the thickness of the entire tungsten layer to be polished is 100 . When the two-step polishing is performed using different slurries of the same material, the scratches generated during polishing can be remarkably suppressed or the scratches already generated can be removed. This is because, even if scratches are generated by the large particles (second abrasive particles) in the main polishing, scratches can be removed by fine polishing using fine particles in the subsequent polishing. Further, in the two-step polishing, the content of the second abrasive grains in the slurry used in the main polishing may be increased to improve the main polishing speed and reduce the polishing time. For example, the content of the second abrasive grains in the slurry used in the main polishing can be increased by 25% or more and increased to 50 or more and 70 or less.
While the preferred embodiments of the present invention have been described and illustrated above using specific terms, such terms are used only for the purpose of clarifying the invention, and the embodiments of the present invention and the described terminology are intended to be illustrative, It will be obvious that various changes and modifications can be made without departing from the spirit and scope of the invention. Such modified embodiments should not be individually understood from the spirit and scope of the present invention, but should be regarded as being within the scope of the claims of the present invention.
Claims (17)
An abrasive for performing polishing;
A dispersing agent for dispersing the abrasive;
An oxidizing agent for oxidizing the tungsten surface; And
And a dislocation adjusting agent for adjusting the zeta potential of the abrasive,
Wherein the abrasive comprises a first abrasive grain having an average size of primary particles not coagulated with each other in a range of 15 nm to 55 nm and a second abrasive grain having an average size of primary particles not coagulated with each other in a range of 120 nm to 230 nm,
Wherein a difference between a maximum primary particle size of the first abrasive particle and a minimum primary particle size of the second abrasive particle is in the range of 60 to 100 nm,
Wherein the dislocation adjusting agent adjusts the zeta potential of the abrasive to -5 mV to -15 mV.
Wherein the abrasive comprises zirconium oxide particles and is contained in the range of 0.1 wt% to 10 wt% with respect to the total weight of the slurry.
Wherein the entire first abrasive grains are smaller than the average primary grain size of the second abrasive grains.
Wherein the difference between the average primary particle size of the first abrasive particles and the average primary particle size of the second abrasive particles is in the range of 90 to 130 nm.
Wherein the average primary particle size of the first abrasive particles is in the range of 20 nm to 50 nm and the average primary particle size of the second abrasive particles is in the range of 130 nm to 180 nm.
Wherein the abrasive agent contains a larger amount of the first abrasive grains than an amount of the second abrasive grains.
Wherein the total amount of the abrasive is 100, and the amount of the second abrasive grains is in the range of 5 to 50 with respect to the whole abrasive.
And the amount of the second abrasive grains is in the range of 15 to 25 with respect to the total abrasive, when the total amount of the abrasive is 100. [
Preparing a substrate on which a tungsten layer is formed;
A first abrasive grain having an average size of primary particles not coagulated with each other in a range of 15 nm to 55 nm and a second abrasive grain having an average size of primary particles not coagulated with each other in a range of 120 nm to 230 nm, Wherein the difference between the maximum size of the primary particles of the particles and the minimum size of the primary particles of the second abrasive particles is in a range of 60 to 100 nm and a slurry comprising a disposing agent to adjust the zeta potential of the abrasive to -5 mV to -15 mV ; And
And polishing the tungsten layer while supplying the slurry onto the substrate.
The step of providing the substrate on which the tungsten layer is formed may include:
Forming a first region having a plurality of first patterns on a substrate and a second region being a region other than the first region; And
And forming a tungsten layer on the first region and the second region.
Wherein the second region has a second pattern different from the first pattern, the density of the first pattern is higher than the density of the second pattern,
Wherein the polishing process includes polishing the tungsten layer of the first region and the tungsten layer of the second region together.
Wherein the tungsten layer of the second region is at least one of a grain size and a layer thickness larger than the tungsten layer of the first region,
Wherein the polishing process includes polishing the tungsten layer of the first region and the tungsten layer of the second region together.
Wherein the abrasive comprises zirconium oxide particles and is contained in the range of 0.1 wt% to 10 wt% with respect to the total weight of the slurry.
And subsequently polishing the tungsten layer while supplying a slurry containing only the first abrasive grains as an abrasive.
The thickness of the entire tungsten layer being polished by the polishing process and the subsequent polishing process is 100, the tungsten layer of 70 to 95 is polished by the polishing process, and the tungsten layer of 5 to 30 is polished by the subsequent polishing process A method of polishing a substrate.
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