JP2010010454A - Polishing composition and polishing method using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polishing composition that is more suitably used in the use of polishing a silicon monocrystalline substrate, and provide a polishing method using the same. <P>SOLUTION: The polishing composition includes abrasive grains, piperazine, strong electrolyte salt, and water. The mole ratio of piperazine to strong electrolyte salt in the polishing composition is in the range from 0.07 to 1.2. The content of piperazine in the polishing composition is 0.02 mol/L or above, and the content of strong electrolyte salt in the polishing composition is 0.03 mol/L or above. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a polishing composition mainly used for polishing a silicon single crystal substrate for a semiconductor integrated circuit and a polishing method using the same.

  For polishing compositions used in applications for polishing silicon single crystal substrates, as with polishing compositions used in other applications, a high polishing rate ( Removal rate). Above all, for polishing compositions used in applications (so-called back polish) for polishing the back surface of a silicon single crystal substrate having a semiconductor wiring formed on the surface, the flatness of the substrate after polishing is high. Instead of being required, having a high polishing rate is more strongly demanded than polishing compositions used in other applications.

Conventionally, for example, the polishing compositions described in Patent Literatures 1 and 2 are known as polishing compositions that can be used for polishing silicon single crystal substrates. The polishing composition of Patent Document 1 contains water, colloidal silica, a water-soluble polymer such as polyacrylamide having a molecular weight of 100,000 or more, a water-soluble salt such as potassium chloride, and an alkaline compound such as ammonia. The polishing composition of Patent Document 2 contains silica particles, basic substances such as water and ammonia, and inorganic salts such as potassium chloride. However, these conventional polishing compositions are insufficient to sufficiently satisfy the above-described requirements regarding the polishing rate of a silicon single crystal substrate, and there is still room for improvement.
Japanese Patent Laid-Open No. 04-063428 International Publication No. 2005/90511 Pamphlet

  Therefore, an object of the present invention is to provide a polishing composition that can be more suitably used in applications for polishing a silicon single crystal substrate, and a polishing method using the same.

  In order to achieve the above object, in one embodiment of the present invention, a polishing composition containing abrasive grains, piperazine, a strong electrolyte salt, and water is provided. The molar ratio of piperazine to strong electrolyte salt in the polishing composition is in the range of 0.07 to 1.2. The content of piperazine in the polishing composition is 0.02 mol / L or more, and the content of the strong electrolyte salt in the polishing composition is 0.03 mol / L or more.

  The zeta potential of the polishing composition is preferably 40 mV or more higher than the zeta potential of a reference slurry comprising the same type and amount of abrasive grains as the abrasive grains in the polishing composition and the remaining water. The pH of the polishing composition is preferably in the range of 10.3 to 11.3. The polishing composition preferably further contains a chelating agent. The chelating agent contained in the polishing composition is preferably an organic phosphonic acid chelating agent.

  In another aspect of the present invention, a polishing method for polishing a silicon single crystal substrate using the above polishing composition is provided.

  ADVANTAGE OF THE INVENTION According to this invention, the polishing composition which can be used more suitably in the use which grind | polishes a silicon single crystal substrate, and the grinding | polishing method using the same are provided.

Hereinafter, an embodiment of the present invention will be described.
The polishing composition of this embodiment is prepared by mixing abrasive grains, piperazine and a strong electrolyte salt with water. Accordingly, the polishing composition contains abrasive grains, piperazine, a strong electrolyte salt, and water. The polishing composition of this embodiment is mainly intended for use in polishing a silicon single crystal substrate, in particular, in polishing a back surface of a silicon single crystal substrate having a semiconductor wiring formed on the surface.

The abrasive grains are blended in the polishing composition to give mechanical polishing performance to the polishing composition.
The type of abrasive grains contained in the polishing composition is not particularly limited. For example, metal oxide particles such as silicon oxide, aluminum oxide, titanium oxide, zirconium oxide, and cerium oxide can be used. . However, when a polishing composition is used for polishing a silicon single crystal substrate, silicon dioxide can be used particularly preferably, and colloidal silica is particularly preferable. When silicon dioxide, especially colloidal silica is used as the abrasive grains, the number of scratches is particularly reduced in the silicon single crystal substrate after polishing with the polishing composition.

  The average particle size (average primary particle size) calculated from the BET specific surface area of the abrasive grains contained in the polishing composition is preferably 10 nm or more, more preferably 30 nm or more, still more preferably 40 nm or more, particularly preferably. Is 50 nm or more. As the average primary particle diameter of the abrasive grains increases, the polishing rate of the silicon single crystal substrate with the polishing composition increases. In this respect, when the average primary particle diameter of the abrasive grains is 10 nm or more, more specifically 30 nm or more, more specifically 40 nm or more, and even more specifically 50 nm or more, the polishing rate of the silicon single crystal substrate by the polishing composition is practically used. Further, it becomes easy to improve to a particularly suitable level.

  The average primary particle size of the abrasive grains contained in the polishing composition is preferably 200 nm or less, more preferably 100 nm or less, still more preferably 80 m or less, and particularly preferably 60 nm or less. As the average primary particle diameter of the abrasive grains decreases, the dispersion stability of the abrasive grains in the polishing composition improves. In this respect, if the average primary particle diameter of the abrasive grains is 200 nm or less, more specifically 100 nm or less, more specifically 80 m or less, and even more preferably 60 nm or less, the dispersion stability of the abrasive grains in the polishing composition is practical. Further, it becomes easy to improve to a particularly suitable level.

  The average particle diameter (average secondary particle diameter) obtained by the dynamic light scattering method of the abrasive grains contained in the polishing composition is preferably 20 nm or more, more preferably 60 nm or more, and still more preferably 80 nm or more. Particularly preferably, it is 90 nm or more. As the average secondary particle diameter of the abrasive grains increases, the polishing rate of the silicon single crystal substrate with the polishing composition increases. In this respect, if the average secondary particle diameter of the abrasive grains is 20 nm or more, more specifically 60 nm or more, more specifically 80 nm or more, and even more specifically 90 nm or more, the polishing rate of the silicon single crystal substrate by the polishing composition is increased. It becomes easy to improve to a level particularly suitable for practical use.

  The average secondary particle diameter of the abrasive grains contained in the polishing composition is preferably 400 nm or less, more preferably 300 nm or less, still more preferably 200 nm or less, and particularly preferably 150 nm or less. As the average secondary particle diameter of the abrasive grains decreases, the dispersion stability of the abrasive grains in the polishing composition improves. In this respect, if the average secondary particle diameter of the abrasive grains is 400 nm or less, more specifically 300 nm or less, more specifically 200 nm or less, and even more specifically 150 nm or less, the dispersion stability of the abrasive grains in the polishing composition is improved. It becomes easy to improve to a level particularly suitable for practical use.

  The content of abrasive grains in the polishing composition is preferably 0.5% by mass or more, more preferably 1.0% by mass or more, further preferably 1.5% by mass or more, and particularly preferably 2.0%. It is at least mass%. As the abrasive grain content increases, the polishing rate of the silicon single crystal substrate with the polishing composition increases. In this regard, the content of abrasive grains in the polishing composition is 0.5% by mass or more, more specifically 1.0% by mass or more, more specifically 1.5% by mass or more, and even more preferably 2.0% by mass. If it is% or more, it becomes easy to improve the polishing rate of the silicon single crystal substrate with the polishing composition to a particularly suitable level for practical use.

  The content of the abrasive grains in the polishing composition is preferably 45% by mass or less, more preferably 20% by mass or less, still more preferably 10% by mass or less, and particularly preferably 5% by mass or less. As the abrasive content decreases, the material cost of the polishing composition decreases, and the dispersion stability of the abrasive grains in the polishing composition improves. In this respect, if the content of abrasive grains in the polishing composition is 45% by mass or less, more specifically 20% by mass or less, more specifically 10% by mass or less, and even more specifically 5% by mass or less, for polishing. It becomes easy to improve the dispersion stability of the abrasive grains in the composition to a particularly suitable level for practical use.

The piperazine is blended in the polishing composition in order to promote the polishing of the silicon single crystal substrate with the polishing composition.
It is essential that the content of piperazine in the polishing composition is 0.02 mol / L or more. When the content of piperazine in the polishing composition is less than 0.02 mol / L, the polishing rate of the silicon single crystal substrate by the polishing composition is generally insufficient for practical use. In order to improve the polishing rate of the silicon single crystal substrate with the polishing composition to a practically particularly suitable level, the content of piperazine in the polishing composition is preferably 0.035 mol / L or more.

  The upper limit of the content of piperazine in the polishing composition is not particularly limited, but it is preferably not more than the maximum amount that can be dissolved in the polishing composition, for example, 1.7 mol / L or less.

The strong electrolyte salt is blended in the polishing composition in order to promote the polishing of the silicon single crystal substrate with the polishing composition.
The type of strong electrolyte salt contained in the polishing composition is not particularly limited, and examples thereof include potassium chloride (KCl), sodium chloride (NaCl), potassium sulfate (K ₂ SO ₄ ), and sodium sulfate (Na ₂ ). Inorganic alkali metal salts such as SO ₄ ) can be used. However, potassium chloride can be used particularly suitably because it is available at low cost and is readily soluble in water.

  It is essential that the content of the strong electrolyte salt in the polishing composition is 0.03 mol / L or more. When the content of the strong electrolyte salt in the polishing composition is less than 0.03 mol / L, the polishing rate of the silicon single crystal substrate by the polishing composition is generally insufficient for practical use. In order to improve the polishing rate of the silicon single crystal substrate with the polishing composition to a practically particularly suitable level, the content of the strong electrolyte salt in the polishing composition should be 0.13 mol / L or more. Preferably, it is 0.23 mol / L or more.

  Further, the upper limit of the content of the strong electrolyte salt in the polishing composition is not particularly limited, but it may be not more than the maximum amount that can be dissolved in the polishing composition, for example, 3.4 mol / L or less. preferable.

  It is essential that the molar ratio of piperazine to the strong electrolyte salt contained in the polishing composition is 0.07 to 1.2. When this molar ratio is out of the above range, the polishing rate of the silicon single crystal substrate with the polishing composition is generally insufficient for practical use. In order to improve the polishing rate of the silicon single crystal substrate with the polishing composition to a practically particularly suitable level, the molar ratio of piperazine to the strong electrolyte salt is preferably 0.13 or more. For the same reason, the molar ratio of piperazine to strong electrolyte salt is preferably 0.6 or less, more preferably 0.26 or less, and still more preferably 0.18 or less.

  The zeta potential of the polishing composition is such that a strong electrolyte salt is contained in the polishing composition, so that the same amount of abrasive grains of the same type as the abrasive grains in the polishing composition and the remaining slurry of water. The value is higher than the zeta potential. The difference between the zeta potential of the polishing composition and the zeta potential of the reference slurry is preferably +40 mV or more, more preferably +50 mV or more. If the content of the strong electrolyte salt in the polishing composition is set so that the difference in zeta potential is +40 mV or more, more specifically +50 mV or more, the polishing rate of the silicon single crystal substrate by the polishing composition is practically used. It becomes easy to improve to a particularly suitable level.

  It is preferable that pH of polishing composition is 10.3 or more, More preferably, it is 10.5 or more. As the pH of the polishing composition increases, the polishing rate of the silicon single crystal substrate with the polishing composition increases. In this respect, if the polishing composition has a pH of 10.3 or higher, more specifically 10.5 or higher, the polishing rate of the silicon single crystal substrate by the polishing composition is improved to a particularly suitable level for practical use. Becomes easy.

  Moreover, it is preferable that pH of polishing composition is 11.3 or less, More preferably, it is 10.8 or less. If the pH of the polishing composition is 11.3 or less, more specifically 10.8 or less, dissolution of abrasive grains in the polishing composition that can occur in a strong alkali region is prevented.

According to this embodiment, the following advantages are obtained.
The polishing composition of the present embodiment contains abrasive grains, piperazine and a strong electrolyte salt, and each content of piperazine and strong electrolyte salt in the polishing composition is set to a predetermined value or more. The molar ratio of piperazine to the strong electrolyte salt in the polishing composition is set within a predetermined range. Therefore, the polishing composition can polish the silicon single crystal substrate at a high removal rate. Therefore, the polishing composition of the present embodiment can be suitably used for polishing a silicon single crystal substrate.

The embodiment may be modified as follows.
-The polishing composition of the said embodiment may further contain a chelating agent. When a chelating agent is further contained, metal contamination of the silicon single crystal substrate by the polishing composition is suppressed. Examples of usable chelating agents include aminocarboxylic acid chelating agents and organic phosphonic acid chelating agents. Aminocarboxylic acid chelating agents include ethylenediaminetetraacetic acid, ethylenediaminetetraacetic acid sodium, nitrilotriacetic acid, nitrilotriacetic acid sodium, nitrilotriacetic acid ammonium, hydroxyethylethylenediaminetriacetic acid, hydroxyethylethylenediaminetriacetic acid sodium salt, diethylenetriaminepentaacetic acid, diethylenetriamine Examples include sodium pentaacetate, triethylenetetramine hexaacetic acid, sodium triethylenetetramine hexaacetate and the like. Organic phosphonic acid chelating agents include 2-aminoethylphosphonic acid, 1-hydroxyethylidene-1,1-diphosphonic acid, aminotri (methylenephosphonic acid), ethylenediaminetetrakis (methylenephosphonic acid), diethylenetriaminepenta (methylenephosphonic acid) Ethane-1,1, -diphosphonic acid, ethane-1,1,2-triphosphonic acid, ethane-1-hydroxy-1,1-diphosphonic acid, ethane-1-hydroxy-1,1,2-triphosphonic acid, Ethane-1,2-dicarboxy-1,2-diphosphonic acid, methanehydroxyphosphonic acid, 2-phosphonobutane-1,2-dicarboxylic acid, 1-phosphonobutane-2,3,4-tricarboxylic acid, α-methylphosphono Contains succinic acid. However, organic phosphonic acid chelating agents that can be used particularly preferably are ethylenediaminetetrakis (methylenephosphonic acid) or diethylenetriaminepenta (methylenephosphonic acid), more preferably ethylenediaminetetrakis (methylenephosphonic acid). is there.

The polishing composition of the above embodiment may further contain additives such as a water-soluble polymer, a surfactant, a pH adjuster, a preservative, an antifungal agent, and a rust preventive as necessary. .
-Each polishing composition of the said embodiment may be prepared by diluting the undiluted | stock solution of polishing composition with water.

  The polishing composition of the above embodiment may be supplied in a one-part type that is stored and stored in one container, or a multi-part including a two-part type that is stored separately in two containers. It may be supplied in molds. In order to store stably over a long period of time, it is preferable to store the abrasive grains and the strong electrolyte salt separately.

Next, the present invention will be described more specifically with reference to examples and comparative examples.
In Examples 1 to 20, colloidal silica, piperazine, a strong electrolyte salt and a chelating agent as abrasive grains were mixed in water to prepare a polishing composition. In Comparative Examples 1 to 9, colloidal silica was mixed with water together with some of piperazine or an alternative compound, a strong electrolyte salt or an alternative compound, and a chelating agent to prepare a polishing composition. Table 1 shows details of piperazine or an alternative compound, a strong electrolyte salt or an alternative compound, and a chelating agent in the polishing composition of each example. Table 1 also shows the results of measuring the pH of the polishing composition of each example and the difference between the zeta potential of each polishing composition relative to the zeta potential of the reference slurry. The colloidal silica contained in the polishing compositions of Examples 1 to 20 and Comparative Examples 1 to 9 has an average primary particle size of 52 nm and an average secondary particle size of 115 nm. Also in the case of the composition for use, the content of colloidal silica is 2.25% by mass. Moreover, all content of the chelating agent in the polishing composition of Examples 1-3, 5-20 and Comparative Examples 2, 3, 7-9 is 0.1 g / L.

In the column of “piperazine or an alternative compound” in Table 1,
PIP is piperazine,
EDA is ethylenediamine,
NH ₃ is ammonia,
DAB is 1,4-diaminobutane,
TMAH is tetramethylammonium hydroxide,
KOH represents potassium hydroxide.

In the column “Strong electrolyte salt or an alternative compound” in Table 1,
KCl is potassium chloride,
NaCl is sodium chloride,
K ₂ SO ₄ is potassium sulfate,
K ₂ CO ₃ represents potassium carbonate (weak electrolyte salt).

In the “chelating agent” column of Table 1,
EDTPO is ethylenediaminetetrakis (methylenephosphonic acid),
DTPA is diethylenetriaminepentaacetic acid,
TTHA represents triethylenetetramine hexaacetic acid.

  Table 1 shows the results of determining the polishing rate when the surface of the silicon single crystal substrate was polished under the conditions shown in Table 2 using the polishing composition of each example based on the difference in weight of the substrate before and after polishing. Shown in the "Polishing rate" column.

An aqueous solution of copper and nickel was added to the polishing composition of each example so that both the copper atom concentration and the nickel atom concentration in the polishing composition were 500 ppb. Using the polishing composition of each example contaminated with metal in this manner, the surface of the silicon single crystal substrate was polished under the conditions shown in Table 2, and the degree of metal contamination was measured on the polished substrate. Specifically, after the polished substrate is cleaned, copper atoms and nickel atoms in the substrate are recovered by vapor phase decomposition (VPD), and a plasma emission analyzer “ICPS-1000IV” manufactured by Shimadzu Corporation is used. And quantified. When the number of copper atoms per unit area of the substrate is 2 × 10 ¹⁰ atoms / cm ² or less, ○ (good), more than 2 × 10 ¹⁰ atoms / cm ^{2 and} 5 × 10 ¹³ atoms / cm ² or less shown in "copper contamination" column of Table 1 is △ (acceptable), the results when 5 × greater than 10 ¹³ atoms / cm ² was evaluated as × (poor) to. Further, when the number of nickel atoms per unit area of the substrate is 3 × 10 ¹⁰ atoms / cm ² or less, ○ (good), more than 3 × 10 ¹⁰ atoms / cm ^{2 and} 2 × 10 ¹¹ atoms / cm ² or less. In the case of △ (possible), when it exceeds 2 × 10 ¹¹ atoms / cm ^2, the result of evaluation as x (defect) is shown in the “nickel contamination” column of Table 1.

  As shown in Table 1, the polishing rate with the polishing compositions of Examples 1 to 20 was higher than the polishing rate with the polishing compositions of Comparative Examples 1 to 9. Moreover, from the results shown in Table 1, it was also clarified that the metal contamination of the substrate by the polishing composition is suppressed by the addition of the chelating agent.

Claims (6)

Containing abrasive grains, piperazine, strong electrolyte salt, and water,
The molar ratio of piperazine to strong electrolyte salt is in the range of 0.07 to 1.2;
Piperazine content is 0.02 mol / L or more,
Polishing composition characterized by content of strong electrolyte salt being 0.03 mol / L or more.   The polishing composition according to claim 1, wherein the zeta potential of the polishing composition is 40 mV or more higher than the zeta potential of a reference slurry comprising the same type and amount of abrasive grains as the abrasive grains in the polishing composition and the remaining water. object.   The polishing composition according to claim 1 or 2, wherein the pH is in the range of 10.3 to 11.3.   The polishing composition according to any one of claims 1 to 3, further comprising a chelating agent.   The polishing composition according to claim 4, wherein the chelating agent is an organic phosphonic acid chelating agent.   A polishing method comprising polishing a silicon single crystal substrate using the polishing composition according to any one of claims 1 to 5.