JP2012216723A - Polishing composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polishing composition which is capable of reducing LPDs and surface roughness.SOLUTION: The polishing composition contains at least one water-soluble polymer represented by general formula (1) and alkali. For example, the water-soluble polymer comprises modified PVA.

Description

  The present invention relates to a polishing composition.

  Polishing of a silicon wafer by CMP (Chemical Mechanical Polishing) realizes high-precision flattening by performing three-stage or four-stage multi-stage polishing. The primary polishing and secondary polishing performed in the first stage and the second stage, respectively, mainly aim at surface smoothing, and a high polishing rate is required.

  In order to achieve a high polishing rate, the shape and size of the abrasive grains, or the amount added is changed, or a basic compound is added. The abrasive described in Patent Document 1 improves the polishing rate by optimizing the shape and specific surface area of colloidal silica.

  Further, it is required not only to improve the polishing rate but also to reduce the surface roughness of the polished wafer. For example, a surface active agent or an organic compound is added to improve the surface roughness. The polishing composition described in Patent Document 2 includes an abrasive and an alkali metal hydroxide, an alkali metal carbonate, an alkali metal hydrogencarbonate, a quaternary ammonium salt, a peroxide as an additive, It contains at least one compound selected from the group consisting of peroxo acid compounds, whereby a smooth polished surface can be formed and the polishing rate can be increased.

  As multi-level polishing is generally performed in order to realize high-precision planarization of the wafer, the difference between the final polishing performed in the final stage of the third stage or the fourth stage and the secondary polishing becomes ambiguous. Also in secondary polishing, polishing characteristics similar to finish polishing are required.

  In addition, water-soluble polymers such as hydroxyethyl cellulose (HEC) and polyvinyl alcohol are generally used for the slurry used in the final polishing step.

JP 2004-140394 A JP 2001-3036 A

  However, when HEC or polyvinyl alcohol is used, there is a problem that the effect of reducing the light point defect (LPD) is small and the effect of reducing the surface roughness is also small.

  Therefore, the present invention has been made to solve such problems, and an object thereof is to provide a polishing composition capable of reducing LPD and surface roughness.

  According to the embodiment of the present invention, the polishing composition has at least one water-soluble high-performance compound selected from vinyl alcohol-based resins having a 1,2-diol structural unit represented by the following general formula (1). Includes molecules and alkali.

  According to an embodiment of the present invention, the polishing composition is at least one water-soluble polymer selected from vinyl alcohol resins having a 1,2-diol structural unit represented by the above formula (1). And an alkali, the reactivity between the water-soluble polymer and the alkali is lowered, and aggregates are hardly generated. In addition, since the water-soluble polymer has good wettability with the silicon wafer, it protects the polished surface of the silicon wafer. As a result, damage to the polished surface of the silicon wafer due to aggregates is reduced.

  Therefore, LPD and surface roughness of the polished silicon wafer can be reduced.

  Embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals and description thereof will not be repeated.

  Polishing composition COMP1 according to an embodiment of the present invention includes at least one water-soluble polymer selected from vinyl alcohol-based resins having a 1,2-diol structural unit represented by the following general formula (1): , Containing abrasive grains and alkali.

  The polishing composition COMP1 is used for polishing silicon.

  The water-soluble polymer is made of, for example, modified PVA (polyvinyl alcohol).

  As the abrasive grains, those commonly used in this field can be used, and examples thereof include colloidal silica, fumed silica, colloidal alumina, fumed alumina, and ceria, and colloidal silica or fumed silica is particularly preferable.

  The alkali consists of one or two of potassium hydroxide, sodium hydroxide, potassium hydrogen carbonate, potassium carbonate, sodium hydrogen carbonate, sodium carbonate, ammonia, ammonium hydrogen carbonate, ammonium carbonate, and tetramethyl ammonium hydroxide.

  The polishing composition COMP1 is prepared by appropriately mixing at least one water-soluble polymer selected from vinyl alcohol resins having a 1,2-diol structural unit represented by the above formula (1), abrasive grains, and alkali. It is made by adding water. Polishing composition COMP1 contains at least one water-soluble polymer, abrasive grains and alkali selected from vinyl alcohol-based resins having a 1,2-diol structural unit represented by the above formula (1). It is made by mixing with water sequentially. As means for mixing these components, means commonly used in the technical field of polishing compositions such as a monogenizer and ultrasonic waves are used.

  Polishing composition COMP1 is set to the range of pH 10-11 as a result of containing an alkali.

  In the embodiment of the present invention, the polishing composition COMP1 may further contain a chelating agent.

  The chelating agent is ethylenediaminetetraacetic acid (EDTA), sodium ethylenediaminetetraacetate, hydroxyethylenediamine triacetic acid (HEDTA), sodium hydroxyethylethylenediamine triacetate, diethylenetriaminepentaacetic acid (DTPA). Pentaacetic Acid), sodium diethylenetriaminepentaacetate, triethylenetetraminehexaacetic acid, sodium triethylenetetraminehexaacetate, nitrilotriacetic acid (NTA), sodium nitrilotriacetate, ammonium nitrilotriacetate, triethylenetriaminepentaacetic acid (TTHA) : Triethylene Triamine Pentaacetic Acid), Hydroxyethyl Imino Diacetic Acid (HIDA), Dihydroxy Ethyl Glycine (DHEG), Ethylene Glycol bis 2-aminoethyl ether tetraacetic acid (EGTA: Ethylene Glycol bis (2-aminoethylether) Tetraacetic Acid), and 1,2-cyclohexanediamine tetraacetic acid: consists (CDTA 1,2-Cyclohezane Diamine Tetraacetic Acid), 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 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-methyl Examples include phosphonosuccinic acid.

  Further, as the acidic chelating agent, carboxylate, sulfonate, acidic phosphate ester salt, phosphonate, inorganic acid salt, alkylamine ethylene oxide adduct, polyhydric alcohol partial ester, carboxylic acid amide, etc. Can be mentioned.

  Examples of the carboxylic acid of the carboxylate include hexanoic acid, octanoic acid, 2-ethylhexanoic acid, nonanoic acid, isononanoic acid, decanoic acid, lauric acid, isodecanoic acid, dodecanoic acid, myristic acid, palmitic acid, stearic acid, Aliphatic monobasic acids such as isostearic acid, undecenoic acid, oleic acid, linoleic acid, linolenic acid, arachidic acid, behenic acid, 12-hydroxystearic acid, ricinoleic acid; malonic acid, succinic acid, glutaric acid, adipic acid, pimelin Aliphatic dibasic acids such as acid, peric acid, azelaic acid, sebacic acid, dodecanedioic acid, brassic acid, alkenyl succinic acid; salicylic acid, alkylsalicylic acid, phthalic acid, isophthalic acid, terephthalic acid, hemimellitic acid, trimellitic acid , Trimesic acid, pyromellitic acid, naphthalenecarboxylic acid, etc. Aromatic carboxylic acids; dimer acids, trimer acids, naphthenic acid, 9 (or 10) - (4-hydroxyphenyl) etc. octadecanoic acid.

  Examples of the sulfonic acid of the sulfonate include petroleum sulfonic acid, alkylbenzene sulfonic acid, α-olefin sulfonic acid, naphthalene sulfonic acid and the like.

  Examples of the acidic phosphate ester of the acidic phosphate salt include (mono or di) phosphate ester of octanol, (mono or di) phosphate ester of lauryl alcohol, (mono or di) phosphate ester of oleyl alcohol, Examples thereof include (mono or di) phosphate ester of butyl alcohol ethoxylate, (mono or di) phosphate ester of oleyl alcohol ethoxylate, and the like.

  Examples of the phosphonic acid of the phosphonate include aminotrimethylene phosphonic acid and 1-hydroxyethylidene-1,1-diphosphonic acid. Examples of the inorganic acid include (poly) phosphoric acid, silicic acid, boric acid and the like.

  Further, the chelating agent is composed of at least one compound selected from the group consisting of the above-described substituents and derivatives.

  The chelating agent prevents the silicon wafer, which is an object to be polished, from being contaminated with metal.

  Furthermore, in the embodiment of the present invention, the polishing composition COMP1 may further contain a nonionic surfactant.

  A nonionic surfactant consists of N, N, N ', N'-tetrakis (polyoxyethylene) (polyoxypropylene) ethylenediamine, for example.

  Further, the polishing composition according to the embodiment of the present invention may be the polishing composition COMP2.

  Polishing composition COMP2 removes abrasive grains from polishing composition COMP1.

  Polishing composition COMP2 is prepared by appropriately mixing water with at least one water-soluble polymer selected from vinyl alcohol resins having a 1,2-diol structural unit represented by the above formula (1) and an alkali. Made by adding. In addition, the polishing composition COMP2 contains at least one water-soluble polymer selected from a vinyl alcohol resin having a 1,2-diol structural unit represented by the above formula (1) and an alkali in order. It is produced by mixing. As means for mixing these components, means commonly used in the technical field of polishing compositions such as a monogenizer and ultrasonic waves are used.

  Polishing composition COMP2 is set to the range of pH 10-11 as a result of containing an alkali.

  In the embodiment of the present invention, the polishing composition COMP2 may further contain the above-described chelating agent.

  Moreover, in embodiment of this invention, polishing composition COMP2 may further contain the nonionic surfactant.

  A nonionic surfactant consists of N, N, N ', N'-tetrakis (polyoxyethylene) (polyoxypropylene) ethylenediamine, for example.

  Hereinafter, the present invention will be described in detail using examples.

  The components of the polishing composition in Examples 1 to 3 and Comparative Examples 1 to 5 are shown in Table 1.

The polishing composition Sample 1 of Example 1 was 95.42% by weight water, 3.0% by weight colloidal silica (abrasive grains), 1.0% by weight K ₂ CO ₃ , and 0.5% by weight. % KOH, 0.03% by weight G-Polymer (OKS-1028 (degree of polymerization: 600): water-soluble polymer) and 0.05% by weight diethylenetriaminepentaacetic acid (DTPA: chelating agent) .

Here, G-Polymer is a specific example of the modified PVA and is a product of Nippon Synthetic Chemical Industry. OKS-1028 is a product model number of G-Polymer. Therefore, in this specification, G-Polymer of the notation “G-Polymer (AAAAAAAA (degree of polymerization: BBB))” represents a product of Nippon Synthetic Chemical Industry Co., Ltd. as a specific example of the modified PVA, and AAAAAAAAA is G -Represents the product model number of Polymer (the same applies hereinafter).
The polishing composition Sample 2 of Example 2 was obtained by replacing the water-soluble polymer of the polishing composition Sample 1 of Example 1 with 0.03% by weight of G-Polymer (OKS-8049 (degree of polymerization: 450)). It is.

  The polishing composition Sample 3 of Example 3 is obtained by replacing the water-soluble polymer of the polishing composition Sample 1 of Example 1 with 0.03% by weight of G-Polymer (AZF8035W (degree of polymerization: 300)). .

  The polishing composition Sample_CP1 of Comparative Example 1 was obtained by replacing the water-soluble polymer of the polishing composition Sample 1 of Example 1 with 0.03% by weight of G-Polymer (OKS-1009 (degree of polymerization: 1200)). It is.

  Polishing composition Sample_CP2 of Comparative Example 2 is obtained by replacing the water-soluble polymer of the polishing composition Sample 1 of Example 1 with 0.03% by weight of polyvinyl alcohol (PVA (degree of polymerization: 500)).

  The polishing composition Sample_CP3 of Comparative Example 3 is obtained by replacing the water-soluble polymer of the polishing composition Sample 1 of Example 1 with 0.03% by weight of polyvinyl alcohol (PVA (polymerization degree: 2000)).

  The polishing composition Sample_CP4 of Comparative Example 4 is obtained by replacing the water-soluble polymer of the polishing composition Sample 1 of Example 1 with 0.03% by weight of polyvinyl alcohol (PVA (polymerization degree: 3500)).

  The polishing composition Sample_CP5 of Comparative Example 5 is obtained by replacing the water-soluble polymer of the polishing composition Sample 1 of Example 1 with 0.03% by weight of HEC.

  In addition, said composition is a composition before dilution, and is diluted and used at the time of grinding | polishing.

(Polishing rate evaluation 1)
Using a polishing apparatus (SPP800S, manufactured by Okamoto Machine Tool Manufacturing Co., Ltd.), the polishing compositions of Examples 1 to 3 and Comparative Examples 1 to 5 were applied at a rate of 600 ml / min to a polishing pad (SUBA ^™ 400, manufactured by Nita Haas). The polishing platen is rotated at a rotational speed of 33 rpm while applying a pressure of 150 (g / cm ² ) to a silicon wafer having a diameter of 12 inches, and the carrier is rotated at a rotational speed of 30 rpm for 5 minutes. Polishing was performed.

  After polishing, the difference in thickness of the silicon wafer removed by polishing was calculated using a non-contact laser displacement meter using a thickness measuring machine (Nanometro 300TT-A, Kuroda Seiko Co., Ltd.). The polishing rate was evaluated by the thickness (μm / min) of the silicon wafer removed by polishing per unit time.

(LPD evaluation)
LPD is performed by using a wafer surface inspection apparatus (LS6600, manufactured by JEOL Engineering), and the number of particles having a particle diameter of 60 nm or more and the number of particles having a size of 80 nm or more present on the polished wafer surface. , And the number of particles having a size of 100 nm or more was measured as the number of particles per wafer.

(Surface roughness evaluation)
For the surface roughness Ra, the surface roughness of the polished wafer was measured using a non-contact surface roughness measuring machine (Wyco NT9300, manufactured by Veeco).

(Slurry foam evaluation)
20 ml of the slurry was placed in a 100 ml shaking tube, and the slurry was shaken for 1 minute with a shaker that shakes at a stroke rate of 50 mm and at a speed of 100 times / minute. Then, the height of the bubble from the liquid surface after standing still for 1 minute was measured.

[Slurry foaming criteria]
○: 0 to 5 mm
Δ: 6 to 20 mm
×: 21 mm or more

(GBIR evaluation)
GBIR (Global Back-Side Ideal Range) was measured by a wafer flatness inspection apparatus Nano Metro 300TT manufactured by Kuroda Seiko Co., Ltd.

  Table 2 shows LPDs of 100 nm or more when polishing silicon wafers using polishing compositions COMP1-1 to COMP1-3, COMP_CP1-1 to COMP_CP1-5 according to Examples 1 to 3 and Comparative Examples 1 to 5. .

  In Table 2, “◯” indicates that the number of LPDs of 100 nm or more is less than 2000, and “x” indicates that the number of LPDs of 100 nm or more is 2000 or more.

  As shown in Table 2, the LPDs of 100 nm or more when the silicon wafer was polished using the polishing compositions Sample 1 to Sample 3 according to Examples 1 to 3 were 1131, 1135, and 917, respectively. LPD is reduced as the polymerization degree of G-Polymer contained in the polishing compositions Sample to Sample 3 decreases. This is because as the degree of polymerization of G-Polymer decreases, the size per molecule decreases, and the molecules are densely adsorbed to the polished surface, thereby protecting the polished surface of the silicon wafer. it is conceivable that.

  On the other hand, when the silicon wafer was polished using the polishing compositions Sample_CP1 to Sample_CP5 according to Comparative Examples 1 to 5, the numbers of LPDs of 100 nm or more were 16033, 12603, 17455, 25240, and 2368, respectively.

  Thus, LPD can be reduced by grind | polishing a silicon wafer using the polishing composition Sample1-Sample3 by Examples 1-3. And polishing composition Sample_CP1 of the comparative example 1 contains G-Polymer (OKS-1009) whose polymerization degree is 1200, and since it has 16033 LPD, G-Polymer (OKS) which has a polymerization degree of less than 1200 is included. -1028, OKS-8049, AZF8035W) 1131, 1135, 917 LPDs have critical significance.

  Table 3 shows the surface roughness when the silicon wafer was polished using the polishing compositions Sample 2, Sample 3, Sample_CP2, Sample_CP3, and Sample CP5 according to Examples 2 and 3 and Comparative Examples 2, 3, and 5.

  In addition, the addition amount in Table 3 represents the addition amount of the water-soluble polymer. In Table 3, “◯” indicates that the surface roughness becomes 0.3 nm or less as the amount of the water-soluble polymer added increases, and “Δ” indicates that the surface increases as the amount of the water-soluble polymer added increases. The roughness does not become 0.3 nm or less, and “x” indicates that the surface roughness hardly decreases with an increase in the amount of the water-soluble polymer added.

  As shown in Table 3, when a silicon wafer using the polishing compositions Sample 2 and Sample 3 according to Examples 2 and 3 was polished, the surface roughness decreased as the amount of the water-soluble polymer added increased. At an addition amount of 90 ppm, they become 0.23 nm and 0.25 nm, respectively.

  On the other hand, when a silicon wafer was polished using the polishing compositions Sample_CP2, Sample_CP3, and Sample_CP5 according to Comparative Examples 2, 3, and 5, the surface roughness was 0.3 nm or less as the amount of the water-soluble polymer added increased. do not become.

  Therefore, the surface roughness can be reduced by using the polishing compositions Sample 2 and Sample 3 according to Examples 2 and 3.

  Table 4 shows the polishing rates when polishing silicon wafers using the polishing compositions Sample 2, Sample 3, Sample_CP1 to Sample_CP5 according to Examples 2 and 3 and Comparative Examples 1 to 5.

  In Table 4, “◯” indicates that the polishing rate is 0.24 μm / min, “Δ” indicates that the polishing rate is about 10% lower than 0.24 μm / min, and “×” "" Indicates that the polishing rate is about 20% lower than 0.24 μm / min.

  As shown in Table 4, when the silicon wafer was polished using the polishing compositions Sample 2, Sample 3, Sample_CP2, Sample_CP3 according to Examples 2 and 3 and Comparative Examples 2 and 3, the polishing rate was 0.24 μm / min. Yes, the polishing rate when the silicon wafer was polished using the polishing compositions Sample_CP1 and Sample_CP4 according to Comparative Examples 1 and 4 was 0.22 μm / min, and the polishing composition Sample_CP5 according to Comparative Example 5 was used as the silicon. The polishing rate when the wafer is polished is 0.21 μm / min.

  Thus, when G-Polymer having a polymerization degree of less than 1200 is used as the water-soluble polymer, the polishing rate is as high as 0.24 μm / min.

  Table 5 shows the amount of GBIR deterioration when polishing silicon wafers using the polishing compositions Sample 2, Sample 3, Sample_CP1 to Sample_CP5 according to Examples 2 and 3 and Comparative Examples 1 to 5.

  In Table 5, “◯” indicates that the GBIR deterioration amount is less than 0.1 μm, and “×” indicates that the GBIR deterioration amount is greater than 0.1 μm.

  As shown in Table 5, when the silicon wafer was polished using the polishing compositions Sample 2, Sample 3, Sample_CP1 to Sample_CP4 according to Examples 2 and 3 and Comparative Examples 1 to 4, the GBIR deterioration amount was less than 0.1 μm. is there. On the other hand, when the silicon wafer is polished using the polishing composition Sample_CP5 according to Comparative Example 5, the GBIR deterioration amount is larger than 0.1 μm.

  Therefore, by using G-Polymer having a degree of polymerization of less than 1200 as the water-soluble polymer, the deterioration of the surface shape of the silicon wafer can be suppressed as compared with the case where HEC is used as the water-soluble polymer.

  Table 6 shows the foaming heights of the polishing compositions Sample 2, Sample_CP2, SampleP_CP3, and Sample_CP5 according to Example 2 and Comparative Examples 2, 3, and 5.

  In addition, the addition amount in Table 6 represents the addition amount of the water-soluble polymer. In Table 6, “◯” indicates that the foaming height is less than 5 mm, and “x” indicates that the foaming height is 5 mm or more.

  As shown in Table 6, the foaming height of the polishing composition Sample 2 according to Example 2 is 1 mm or less. On the other hand, the foaming heights of the polishing compositions Sample_CP2, Sample_CP3, and Sample_CP5 according to Comparative Examples 2, 3, and 5 are 5 mm or more.

  Therefore, the foaming height of the polishing composition can be greatly reduced by using G-Polymer (OKS-8049) having a polymerization degree of less than 1200 as the water-soluble polymer.

  As described above, by using G-Polymer (OKS-1028, OKS-8049, AZF8035W) having a polymerization degree of less than 1200 as a water-soluble polymer, 100 nm or more of LPD can be suppressed to less than 2000, and The surface roughness of the silicon wafer can be reduced to 0.3 nm or less.

  However, the polishing compositions Sample_CP1 to Sample_CP5 according to Comparative Examples 1 to 5 cannot achieve both suppression of the LPD of 100 nm or more to less than 2000 and reduction of the surface roughness of the silicon wafer to 0.3 nm or less. .

  And polishing composition Sample2 by Example 2 can reduce foaming height significantly compared with polishing composition Sample_CP2, Sample_CP3, Sample_CP5 by comparative example 2,3,5.

  Table 7 shows the compositions of the polishing compositions Sample 4, Sample_CP6, and Sample_CP7 according to Example 4 and Comparative Examples 6 and 7.

The polishing composition Sample 4 of Example 4 is composed of 98.42% by weight of water, 1.0% by weight of K ₂ CO ₃ , 0.5% by weight of KOH, and 0.03% by weight of G-Polymer. (OKS-8049 (degree of polymerization: 450): water-soluble polymer) and 0.05% by weight of diethylenetriaminepentaacetic acid (DTPA: chelating agent). That is, the polishing composition Sample 4 of Example 4 is obtained by deleting the colloidal silica (abrasive grains) of the polishing composition Sample 2 of Example 2.

  The polishing composition Sample_CP6 of Comparative Example 6 is obtained by replacing the water-soluble polymer of the polishing composition Sample 4 of Example 4 with 0.03% by weight of polyvinyl alcohol (PVA (degree of polymerization: 500)).

  The polishing composition Sample_CP7 of Comparative Example 7 is obtained by replacing the water-soluble polymer of the polishing composition Sample 4 of Example 4 with 0.03% by weight of HEC.

  As described above, the polishing compositions Sample 4, Sample_CP6 and Sample_CP7 according to Example 4 and Comparative Examples 6 and 7 are polishing compositions that do not contain abrasive grains.

  In addition, said composition is a composition before dilution, and is diluted and used at the time of grinding | polishing.

  Table 8 shows the LPD of 80 nm or more, the LPD of 100 nm or more, and the polishing rate when a silicon wafer was polished using the polishing compositions Sample 4, Sample_CP6, and Sample_CP7 according to Example 4 and Comparative Examples 6 and 7.

  The polishing rate was evaluated by the method described in the polishing rate evaluation 1 described above.

  As shown in Table 8, when the silicon wafer was polished using the polishing composition Sample 4 according to Example 4, the number of LPDs of 80 nm or more was 48, and the number of LPDs of 100 nm or more was 22, and the polishing rate. Is 0.05 μm / min.

  On the other hand, when a silicon wafer was polished using the polishing composition Sample_CP6 according to Comparative Example 6, the number of LPDs of 80 nm or more and LPD of 100 nm or more was more than 30000, and the polishing rate was 0.05 μm / min. Further, when the silicon wafer was polished using the polishing composition Sample_CP7 according to Comparative Example 7, the number of LPDs of 80 nm or more was 69, the number of LPDs of 100 nm or more was 22, and the polishing rate was 0.07 μm. / Min.

  Thus, in a polishing composition that does not contain abrasive grains, PVA or HEC is used as the water-soluble polymer by using G-Polymer (OKS-8049) having a polymerization degree of less than 1200 as the water-soluble polymer. The LPD can be reduced while maintaining the polishing rate in the case of the above.

  As described above, the polishing compositions Sample 1 to Sample 4 according to Examples 1 to 4 are polishing compositions using G-Polymer having a polymerization degree of less than 1200 as a water-soluble polymer, and Examples 1 to 4 are used. The LPD and surface roughness when a silicon wafer is polished using the polishing compositions Sample 1 to Sample 4 according to the above can be reduced. The range in which the degree of polymerization of G-Polymer as the water-soluble polymer is less than 1200 is a range suitable when the polishing compositions Sample 1 to Sample 4 according to Examples 1 to 4 are used for secondary polishing of a silicon wafer. It is.

  Table 9 shows the compositions of the polishing compositions Sample 5 to Sample 8 and Sample_CP8 to Sample_CP10 according to Examples 5 to 8 and Comparative Examples 8 to 10.

The polishing composition Sample 5 of Example 5 is composed of 89.25 wt% water, 10.5 wt% colloidal silica (abrasive grains), 0.1 wt% NH ₃ , and 0.15 wt% G-Polymer (OKS-1083 (degree of polymerization: 1900): water-soluble polymer).

The polishing composition Sample 6 of Example 6 was obtained by changing the NH ₃ content of the polishing composition Sample 5 of Example 5 to 0.2 wt%.

The polishing composition Sample 7 of Example 7 was obtained by changing the NH ₃ content of the polishing composition Sample 5 of Example 5 to 0.3% by weight.

The polishing composition Sample 8 of Example 8 was obtained by changing the NH ₃ content of the polishing composition Sample 5 of Example 5 to 0.4 wt%.

The polishing composition Sample_CP8 of Comparative Example 8 was obtained by changing the NH ₃ content of the polishing composition Sample 5 of Example 5 to 0.6% by weight.

Polishing composition Sample_CP9 of Comparative Example 9 was obtained by changing the NH ₃ content of the polishing composition Sample 5 of Example 5 to 0.8% by weight.

Polishing composition Sample_CP10 of Comparative Example 10 was obtained by changing the NH ₃ content of the polishing composition Sample 5 of Example 5 to 1.0% by weight.

  Polishing compositions Sample 5 to Sample 8 according to Examples 5 to 8 are polishing compositions used for polishing the final stage of a silicon wafer.

  In addition, said composition was a composition before dilution, and the grinding | polishing characteristic was evaluated using the polishing composition diluted 30 times.

(Polishing rate evaluation 2)
Using a polishing apparatus (Strasbaugh), the polishing compositions of Examples 5 to 8 and Comparative Examples 8 to 10 were supplied to the polishing pad (Supreme RN-H) at a rate of 300 ml / min, and silicon having a diameter of 8 inches was used. Polishing was performed for 5 minutes while rotating the polishing platen at a rotation speed of 115 rpm while applying a pressure of 100 (g / cm ² ) to the wafer and rotating the carrier at a rotation speed of 100 rpm.

  After polishing, the polishing rate was evaluated by the method described in Polishing rate evaluation 1.

  Table 10 shows the LPD, Haze and polishing rate of 60 nm or more when polishing silicon wafers using the polishing compositions Sample 5 to Sample 8 and Sample_CP8 to Sample_CP10 according to Examples 5 to 8 and Comparative Examples 8 to 10.

  When a silicon wafer was polished using the polishing compositions Sample 5 to Sample 8 according to Examples 5 to 8, the LPDs of 60 nm or more were 344, 199, 273, and 290, respectively, and the Haze was 104, 102, 107, 113, and the polishing rates are 17 (nm / min), 20 (nm / min), 23 (nm / min), and 24 (nm / min), respectively.

  On the other hand, when a silicon wafer was polished using the polishing compositions Sample_CP8 to Sample_CP10 according to Comparative Examples 8 to 10, the LPDs of 60 nm or more were 731 pieces, 1996 pieces, and 637 pieces, respectively, and Haze was respectively 126, 136, and 136, and the polishing rates are 28 (nm / min), 29 (nm / min), and 31 (nm / min), respectively.

  Thus, when a silicon wafer was polished using the polishing compositions Sample 5 to Sample 8 according to Examples 5 to 8, a large decrease in the polishing rate was prevented, and an LPD of 60 nm or more increased from 0.455 to 0.099. The haze can be reduced to 0.89 to 0.75 times.

  Table 11 shows the compositions of the polishing compositions Sample 9 to Sample 14, Sample_CP11, and Sample_CP12 according to Examples 9 to 14 and Comparative Examples 11 and 12.

Polishing Composition Sample 9 according to Example 9 was 88.85 wt% water, 10.5 wt% colloidal silica (abrasive grains), 0.4 wt% NH ₃ , and 0.25 wt% G-Polymer (OKS-1083 (degree of polymerization: 1900): water-soluble polymer).

  Polishing composition Sample 10 according to Example 10 was added to polishing composition Sample 9 according to Example 9 with 0.1% by weight of N, N, N ′, N′-tetrakis (polyoxyethylene) (polyoxypropylene) ethylenediamine. Is added.

  Polishing composition Sample 11 according to Example 11 has a content of N, N, N ′, N′-tetrakis (polyoxyethylene) (polyoxypropylene) ethylenediamine of 0.2 according to Polishing composition Sample 10 according to Example 10. The weight is changed.

  Polishing composition Sample 12 according to Example 12 contained 0.3, N, N, N ′, N′-tetrakis (polyoxyethylene) (polyoxypropylene) ethylenediamine in the polishing composition Sample 10 according to Example 10. The weight is changed.

  Polishing composition Sample 13 according to Example 13 has a content of N, N, N ′, N′-tetrakis (polyoxyethylene) (polyoxypropylene) ethylenediamine in the polishing composition Sample 10 according to Example 10 of 0.4. The weight is changed.

  Polishing composition Sample 14 according to Example 14 has a content of N, N, N ′, N′-tetrakis (polyoxyethylene) (polyoxypropylene) ethylenediamine of polishing composition Sample 10 according to Example 10 of 0.5. The weight is changed.

  Polishing composition Sample_CP11 according to Comparative Example 11 has a content of N, N, N ′, N′-tetrakis (polyoxyethylene) (polyoxypropylene) ethylenediamine in the polishing composition Sample 10 according to Example 10 of 0.75. The weight is changed.

  Polishing composition Sample_CP12 according to Comparative Example 12 has a content of N, N, N ′, N′-tetrakis (polyoxyethylene) (polyoxypropylene) ethylenediamine in the polishing composition Sample 10 according to Example 10 of 1.0. The weight is changed.

  Table 12 shows the LPD, Haze and polishing rate of 60 nm or more when a silicon wafer was polished using the polishing compositions Sample 10 to Sample 15, Sample_CP11 and Sample_CP12 according to Examples 9 to 14 and Comparative Examples 11 and 12.

  The polishing rate was evaluated by the method described in the polishing rate evaluation 2 described above.

  As shown in Table 12, when a silicon wafer was polished using the polishing compositions Sample 10 to Sample 15 according to Examples 10 to 15, LPDs of 60 nm or more had 139, 79, 83, 96, 112 and 208, Haze is 113, 113, 112, 112, 111, 112, respectively, and polishing rates are 21 (nm / min), 21 (nm / min), and 16 (nm), respectively. / Min), 18 (nm / min), 11 (nm / min), 9 (nm / min).

  On the other hand, when silicon wafers were polished using the polishing compositions Sample_CP11 and Sample_CP12 according to Comparative Examples 11 and 12, the LPDs of 60 nm or more were 722 and 1366, respectively, and the Haze was 126 and 116, respectively. The polishing rates are 9 (nm / min) and 6 (nm / min), respectively.

  Thus, when the content of N, N, N ′, N′-tetrakis (polyoxyethylene) (polyoxypropylene) ethylenediamine is in the range of 0 to 0.5% by weight, the number of LPDs of 60 nm or more is 208 or less. And N, N, N ′, N′-tetrakis (polyoxyethylene) (polyoxypropylene) ethylenediamine has a content of 0.29 to 0.058 times that of 0.75% by weight or more. Reduced.

  The polishing composition Sample 10 according to Example 10 does not contain N, N, N ′, N′-tetrakis (polyoxyethylene) (polyoxypropylene) ethylenediamine, so that N, N, By setting the content of N ′, N′-tetrakis (polyoxyethylene) (polyoxypropylene) ethylenediamine in the range of 0.1 wt% to 0.4 wt%, the LPD of 60 nm or more is increased from 139 to 112 wt%. The content of N, N, N ′, N′-tetrakis (polyoxyethylene) (polyoxypropylene) ethylenediamine in the polishing composition can be reduced to 0.1 wt% to 0.3 wt%. By setting the range, the number of LPDs of 60 nm or more can be reduced from 139 to 96 or less.

  Therefore, in the polishing composition according to the embodiment of the present invention, the content of the nonionic surfactant (N, N, N ′, N′-tetrakis (polyoxyethylene) (polyoxypropylene) ethylenediamine) is 0.5 wt% or less, preferably 0.1 wt% to 0.4 wt%, more preferably 0.1 wt% to 0.3 wt%. Is done.

Polishing composition A containing a water-soluble polymer composed of G-Polymer, an alkali composed of NH ₃ , and abrasive grains composed of colloidal silica, a water-soluble polymer composed of HEC, an alkali composed of NH ₃ , A filtering experiment was performed on the polishing composition B containing abrasive grains made of colloidal silica. In this case, the polishing compositions A and B are made of a slurry after dilution, G-Polymer is made of a trade name (OKS-1083), and the molecular weight of HEC is 1 million.

  In the filtering experiment, the polishing composition A and B was passed through a filter (0.2 μm @ 10 inches, manufactured by Nippon Pole Co., Ltd.) by rotating a pump (LEV50 (manufactured by Iwaki Co., Ltd.)) at a rotational speed of 4000 rpm. The measurement was performed by measuring the relationship between the elapsed time after dilution and the flow rates of the polishing compositions A and B.

  Table 13 shows the relationship between the elapsed time after dilution and the flow rates of the polishing compositions A and B.

  As shown in Table 13, the flow rate of the polishing composition A using G-Polymer as the water-soluble polymer was 1680 ml / min immediately after dilution, 2040 ml / min after 10 minutes, and 20 minutes. 2070 ml / min at an elapsed time of ˜10080 minutes.

  On the other hand, the flow rate of the polishing composition B using HEC as the water-soluble polymer is 0 ml / min immediately after dilution.

  Therefore, it was found that the use of G-Polymer as the water-soluble polymer suppresses the generation of coarse particles due to pH fluctuation during dilution.

  As described above, LPD and surface roughness can be reduced by using a water-soluble polymer composed of G-Polymer. This is due to the following reason.

  The polymer of PVA is a copolymer of polyvinyl alcohol represented by the following formula (2) and polyvinyl acetate represented by the following formula (3).

  On the other hand, G-Polymer is a copolymer of polyvinyl alcohol represented by the above formula (2) and a modified PVA represented by the following formula (4), and the modified PVA represented by the formula (4): The percentage of is several percent.

  G-Polymer has a site that is more likely to cause steric hindrance than its structure and crystallization is suppressed.

  On the other hand, the polymer of PVA is a polymer having stereoregularity and high crystallinity. The side chain hydroxyl group of PVA is almost the same size as the hydrogen group, and the main chain takes a zigzag chain when crystallized, but the hydroxyl group becomes a steric hindrance and does not have the influence to change its arrangement form. The reason is considered to be the reason.

  Moreover, when PVA is stirred at high speed during polishing or the like, molecular orientation advances and crystallization occurs. As the crystallization of PVA progresses, not only will the scratched surface of the silicon wafer be damaged by fine precipitated crystals, but the polished surface of the silicon wafer may be sufficiently protected by reducing the proportion of water-soluble polymer present. become unable.

  Therefore, when G-Polymer is used as the water-soluble polymer, LPD and surface roughness can be reduced. When a polymer of PVA is used as the water-soluble polymer, the value of LPD is deteriorated or the surface roughness is low. It is thought that it is not removed sufficiently.

  Moreover, in the reactivity with an alkali, there exists the following difference between G-Polymer, PVA, and HEC.

  Cellulose (HEC) and PVA, which are commonly used as wetting agents for silicon abrasives, are reactive with alkali. When mixed, hydroxyl ions are attracted to alkali ions, and the hydroxyl groups of polymer molecules are dehydrated and condensed. It becomes hydrophobic and aggregates and precipitates. In addition, polyether polymers such as poloxamine are precipitated by molecular water crystallized by alkali ions and cannot be dissolved or dispersed in water.

  On the other hand, G-Polymer has low reactivity with alkali, and aggregates are not observed even when alkali is added under the same conditions.

  An aqueous solution containing 1% G-Polymer, an aqueous solution containing 1% HEC, an aqueous solution containing 1% PVA, an aqueous solution containing 1% G-Polymer and 49% KOH, 1% HEC and 49% Table 14 shows the results of measurement of scattering intensity for an aqueous solution containing KOH and an aqueous solution containing 1% PVA and 49% KOH.

  The scattering intensity was measured using ELS-Z2 (ND filter: 0.5%) manufactured by Otsuka Electronics.

  In the case of an aqueous solution not containing alkali (KOH), the scattering intensity does not differ greatly between G-Polymer, HEC and PVA.

  On the other hand, the scattering intensity of the aqueous solution containing G-Polymer and alkali (KOH) is 3397 cps, whereas the scattering intensity of the aqueous solution containing PVA and alkali (KOH) is as large as 252060. Further, in an aqueous solution containing HEC and alkali (KOH), aggregates formed on the water surface immediately after the addition of KOH, and the dispersion was not dispersed in the solution, so that the scattering intensity could not be measured.

  As described above, it has been experimentally demonstrated that G-Polymer has low reactivity with alkali and does not generate aggregates, and PVA and HEC have high reactivity with alkali and generate aggregates. This has been demonstrated experimentally.

  This is because PVA is oriented in an aqueous solution, and alkali ions are efficiently dehydrated in a state where molecules and hydroxyl groups are close to each other, whereas G-Polymer shows a non-uniform distribution in the solution. At the same time, it is difficult to cause dehydration condensation due to the large intermolecular distance in the solution.

  HEC is manufactured from a process in which timber is a raw material, cellulose is extracted from pulp, and cellulose is decomposed and hydroxyethylated by chemical treatment. Schematically, HEC is manufactured by crushing large chunks to create small chunks.

  On the other hand, G-Polymer is produced by connecting a lump of molecular size one by one.

  Therefore, HEC has a three-dimensional solid network structure, whereas G-Polymer has a linear linear structure.

  Thus, celluloses (HEC) are also a three-dimensional network structure, and when the adjacent hydroxyl groups are dehydrated and aggregated by alkali and the amount of alkali (ammonia) added increases, the wettability of the silicon wafer decreases.

  On the other hand, alkali has a polishing promoting action / pH adjusting action (aggregation stability improvement at Z potential) and is a necessary substance for polishing, but as described above, there is a problem in reactivity with the polymer, There is a problem that the range of alkali concentrations that can be used, the variety, and the like are limited by the fact that the alkali itself is adsorbed to the silicon wafer and polymer adhesion (wetting) is reduced.

However, when G-Polymer is used, since the LPD is 199 to 344 (see Tables 9 and 10) when the content of alkali (NH ₃ ) is 0.4% by weight (see Tables 9 and 10), the above problem can be solved.

  As described above, G-Polymer suppresses crystallization and has low reactivity with an alkali, and thus hardly produces an aggregate. On the other hand, PVA and HEC are easy to crystallize and have high reactivity with alkalis, so aggregates are likely to be formed.

  G-Polymer has good wettability with a silicon wafer, whereas PVA has poor wettability with a silicon wafer. HEC has good wettability with a silicon wafer, but a suitable pH range and alkali species that can maintain wettability are limited.

  Due to these differences, when G-Polymer is used as the water-soluble polymer, the polished surface of the silicon wafer is protected by G-Polymer, and damage to the polished surface of the silicon wafer due to aggregates is reduced. Therefore, when G-Polymer is used as the water-soluble polymer, LPD and surface roughness can be reduced.

  In addition, G-Polymer has a linear linear structure in which one molecule-sized mass is connected one by one, whereas HEC has a three-dimensional network structure.

  Due to these structural differences, when G-Polymer is used as the water-soluble polymer, it is considered that the filtering characteristics are good.

  Thus, when a silicon wafer is polished using a polishing composition containing G-Polymer and an alkali, LPD and surface roughness can be reduced. Therefore, the polishing composition according to the embodiment of the present invention is It is sufficient if it contains at least one water-soluble polymer selected from vinyl alcohol resins having a 1,2-diol structural unit represented by the formula (1) and an alkali.

  Further, when a silicon wafer is polished using a polishing composition containing G-Polymer, alkali and abrasive grains, the polishing rate can be increased to reduce LPD and surface roughness (see Tables 2 to 4). A polishing composition according to an embodiment of the present invention includes at least one water-soluble polymer selected from vinyl alcohol-based resins having a 1,2-diol structural unit represented by the above formula (1), an alkali And abrasive grains.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is shown not by the above description of the embodiments but by the scope of claims for patent, and is intended to include meanings equivalent to the scope of claims for patent and all modifications within the scope.

  The present invention is applied to a polishing composition.

Claims (4)

At least one water-soluble polymer selected from vinyl alcohol-based resins having a 1,2-diol structural unit represented by the following general formula (1);
Polishing composition containing an alkali.

  The polishing composition according to claim 1, further comprising abrasive grains.   The polishing composition according to claim 2, further comprising a chelating agent.   The polishing composition according to claim 2, further comprising a nonionic surfactant.