SLURRY COMPOSITION FOR POLISHING SILICON OXIDE FILM, AND POLISHING METHOD USING SAME

Abstract

Proposed are a CMP slurry composition and a polishing method using the same. The CMP slurry composition in which the zeta potential of colloidal silica serving as an abrasive is properly controlled and metal impurities are removed from the colloidal silica and to a polishing method using the same. The CMP slurry composition is configured to improve a polishing performance for a silicon oxide film, minimize scratches on a finished surface, and to enable adjustment of a content ratio of an abrasive and an additive in the composition, thereby enabling adjustment of a polishing selectivity among a silicon oxide film, a silicon nitride film, and a polysilicon film.

Claims

1. A CMP slurry composition configured to adjust a polishing selectivity of a silicon oxide film or a polysilicon film with respect to a silicon nitride film, the CMP slurry composition comprising: 0.2% to 10% by weight of an abrasive composed of colloidal silica; 0.001% to 7% by weight of an additive composed of 5-methylbenzotriazole or polyethylene glycol; and the remainder being a solvent.

2. The CMP slurry composition of claim 1, wherein the additive comprises polyethylene glycol and 5-methylbenzotriazole that are present in a content ratio of 0 to 5.0:an integer higher than 0 to 5.0, and the polishing selectivity ratio of the silicon oxide film:the silicon nitride film: the polysilicon film is in a range of 1 to 50:1:1 to 10.

3. The CMP slurry composition of claim 2, wherein the colloidal silica has a zeta potential of +10 to +70 mV.

4. The CMP slurry composition of claim 3, wherein the colloidal silica has a zeta potential of +15 to +50 mV.

5. The CMP slurry composition of claim 1, wherein the colloidal silica has a particle size of 10 to 120 nm.

6. The CMP slurry composition of claim 5, wherein the particle size is within a range of 30 to 80 nm.

7. The CMP slurry composition of claim 1, wherein the removal rate of the silicon oxide film is within a range of 200 to 3000/min.

8. The CMP slurry composition of claim 1, wherein the colloidal silica contains a metal (Li, B, Mg, K, Ca, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Zr, Mo, Ag, Cd, Sn, Ta, W, Pt, Na, and Al) in concentration of 100 ppb or less.

9. The CMP slurry composition of claim 1, wherein the metal (Li, B, Mg, K, Ca, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Zr, Mo, Ag, Cd, Sn, Ta, W, Pt, Na, and Al) is contained in a concentration of 50 ppb or less.

10. The CMP slurry composition of claim 1, wherein the CMP slurry composition has a pH of 3 to 5.

11. A polishing method using the CMP slurry composition of claim 1 in a method of manufacturing a 3D NAND flash semiconductor device, the polishing method being used to remove an initial step height of a silicon oxide film during a gate gap polysilicon processing process, the polishing method comprising: simultaneously polishing a silicon nitride film and at least one film selected between a silicon oxide film and a polysilicon film.

12. The polishing method of claim 11, wherein the simultaneously polishing is performed by adjusting a polishing selectivity ratio of the silicon oxide film:the silicon nitride film: the polysilicon film by adjusting a content ratio of the abrasive and the additive.

Description

MODE FOR CARRYING OUT THE INVENTION

Examples 1 to 6

[0055] Slurry compositions were prepared according to the components, content ratios, zeta potential values, and pH values listed in Table 1. First, colloidal silica was prepared as an abrasive. Deionized water as a solvent was mixed with an additive containing polyethylene glycol and 5methyl-benzotriazole to adjust the zeta potential value and the content of the abrasive. In this way, CMP slurry compositions that can improve a polishing performance for a silicon oxide film and can adjust a selectivity of the silicon oxide film with respect to a silicon nitride film were prepared. KOH or HNO.sub.3 was added to the prepared CMP slurry compositions as a pH adjuster so that the pH of each CMP slurry composition was adjusted to 3.5.

Comparative Examples 1 and 2

[0056] Slurry compositions were prepared with the components, content ratios, zeta potential values, and pH values listed in Table 1. The slurry compositions of the comparative examples were prepared in the same manner as in Examples 1 to 6 except that the zeta potential value was adjusted to a negative value.

TABLE-US-00001 TABLE 1 Additive (% by weight) Colloidal silica Heterocyclic Zeta compound potential (% by Polyethylene (5methyl- value (mV) weight) glycol benzotriazole) pH Example 1 +15 3 0.5 0.025 3.5 Example 2 +30 3 0.5 0.025 3.5 Example 3 +50 3 0.5 0.025 3.5 Example 4 +15 6 0.5 0.025 3.5 Example 5 +30 6 0.5 0.025 3.5 Example 6 +50 6 0.5 0.025 3.5 Comparative −20 3 0.5 0.025 3.5 Example 1 Comparative −35 3 0.5 0.025 3.5 Example 2

[0057] Measurement of Characteristics (Evaluation of Polishing Rate for Each CMP Slurry Composition)

[0058] The polishing rates of a silicon oxide film and a silicon nitride film for each of the CMP slurry compositions prepared in Examples 1 to 6 and Comparative Examples 1 and 2 were evaluated.

[0059] For the evaluation, as a polishing apparatus, a CMP apparatus manufactured by CTS Co. was used.

[0060] The measurement results of the polishing rates of the silicon oxide film and the silicon nitride film when the prepared CMP slurry compositions are used are shown in Table 2 below.

TABLE-US-00002 TABLE 2 Removal Rate (Polishing Rate, Å/min) Selectivity of silicon Silicon Silicon oxide film to silicon oxide film nitride film nitride film Example 1 400 38 10.5:1 Example 2 550 35 15.7:1 Example 3 630 26 24.2:1 Example 4 650 40 16.3:1 Example 5 890 39 22.8:1 Example 6 1010 35 28.9:1 Comparative 70 680   1:9.7 Example 1 Comparative 50 750    1:15 Example 2

[0061] Comparing Examples 1 to 6 and Comparative Examples 1 and 2, as shown in Table 2, when the zeta potential of the colloidal silica serving as an abrasive had a positive value, it was confirmed that the polishing selectivity of the silicon oxide film to the silicon nitride film increased.

[0062] However, it was confirmed that the polishing selectivity of the silicon nitride film to the silicon oxide film was increased when the zeta potential had a negative value.

[0063] When comparing the results of Examples 1 to 3 corresponding to the cases where the zeta potential had a positive value and was increased from 15 to 30 to 50, the removal rate of the silicon nitride film decreased, and the removal rate of the silicon oxide film increased. Thus, it was confirmed that the selectivity increased. The same conclusions can be made from the comparison among the results of Examples 4 to 6 corresponding to the cases where the zeta potential value has a positive value and was increased from 15 to 30 to 50, the removal rate of the silicon nitride film decreased, and the removal rate of the silicon oxide film increased. That is, the selectivity between the silicon nitride film and the silicon oxide film increased.

[0064] On the other hand, when comparing the results of Examples 1 and 4 in which the content of the abrasive was increased from 3 to 6 with the zeta potential value fixed, it was confirmed that the removal rate of the silicon oxide film increased and thus the selectivity of the silicon oxide film increased. The same conclusion could be made through comparison between the results of Examples 2 and 5 and comparison between the results of Examples 3 and 6 in which the content of the abrasive was also increased from 3 to 6. That is, the removal rate of the silicon oxide film increased and thus the selectivity of the silicon oxide film to the silicon nitride film increased, with an increase of the content of the abrasive from 3 to 6.

[0065] In conclusion, with the use of the composition of the present invention in which the positive value of the zeta potential of the colloidal silica is increased or the content of the abrasive is increased, it is possible to increase the polishing rate of the silicon oxide film at an initial stage of the process so that the silicon oxide film initially having a high aspect ratio can be rapidly polished.

[0066] In addition, since the silicon oxide film can be polished with a high polishing selectivity with respect to the silicon nitride film, the CMP slurry composition of the present invention can be usefully applied to a semiconductor manufacturing process (for example, a gate gap polysilicon processing process) that requires selective removal of a silicon oxide film.

Example 7

[0067] A high-purity colloidal silica from which metal impurities were removed was prepared, and a CMP slurry composition was prepared in the same manner as in Example 2.

Comparative Example 3

[0068] A CMP slurry composition was prepared in the same manner as in Example 7 except that general colloidal silica from which metal impurities were not removed was used.

[0069] The contents of metal impurities, the contents of components constituting a CMP slurry component, composition ratios of the components, and zeta potential values were set as shown in Table 3 below.

TABLE-US-00003 TABLE 3 Zeta potential value of colloidal silica: +30 mV Additive (% by weight) (% by Polyethylene Heterocyclic compound Number of Fe Al weight) glycol (5methyl-benzotriazole) scratches (ea) Example 7 30 ppb 80 ppb 3 0.5 0.025 5 Comparative 11 ppm 520 ppm 3 0.5 0.025 17 Example 3

[0070] Measurement of Characteristics (Evaluation of Polishing Rate for Each CMP Slurry Composition)

[0071] Table 3 shows the number of scratches counted using AIT-XP after a silicon oxide film was polished using each of the CMP slurry compositions prepared as in Example 7 and Comparative Example 3.

[0072] When the silicon oxide film was polished with the slurry composition of Example 7, the number of scratches was significantly reduced compared to the case where the silicon oxide film was polished with the slurry composition of Comparative Example 3.

[0073] As a result, the composition of the present invention using the colloidal silica from which metal impurities are removed minimizes scratch defects of the silicon oxide film, thereby improving process reliability and productivity.

Examples 8 to 12

[0074] Slurry compositions were prepared according to the components, content ratios, zeta potential values, and pH values listed in Table 4. First, colloidal silica was prepared as an abrasive. Deionized water as a solvent was mixed with an additive containing polyethylene glycol and 5methyl-benzotriazole to adjust the zeta potential value and the content of the abrasive. In this way, CMP slurry compositions that can improve a polishing performance for a silicon oxide film and can adjust a selectivity of the silicon oxide film with respect to a silicon nitride film were prepared. KOH or HNO.sub.3 was added to the prepared CMP slurry compositions as a pH adjuster so that the pH of each CMP slurry composition was adjusted to 3.5.

Comparative Examples 4 to 5

[0075] The slurry compositions of Comparative Examples 4 and 5 were prepared in the same manner as in Examples 8 to 12 except that the slurry composition of Comparative Example 4 did not use polyethylene glycol and the slurry composition of Comparative Example 5 did not use 5methyl-benzotriazole which is a heterocyclic compound. In each of the CMP slurry compositions, the type of colloidal silica and the content of the colloidal silica were the same.

[0076] The content of the colloidal silica contained in the prepared CMP slurry compositions is shown in Table 4 below.

TABLE-US-00004 TABLE 4 Additive (% by weight) Colloidal silica Heterocyclic Zeta compound potential (% by Polyethylene (5methyl- value (mV) weight) glycol benzotriazole) pH Example 8 +30 3 0.5 0.025 3.5 Example 9 +30 3 0.2 0.025 3.5 Example 10 +30 3 1.4 0.025 3.5 Example 11 +30 3 0.5 0.01 3.5 Example 12 +30 3 0.5 0.05 3.5 Comparative +30 3 0 0.025 3.5 Example 4 Comparative +30 3 0.5 0 3.5 Example 5

[0077] Measurement of Characteristics (Evaluation of Polishing Rate for Each CMP Slurry Composition)

[0078] The polishing rates of a silicon oxide film, a silicon nitride film, and a polysilicon film for each of the CMP slurry compositions prepared in Examples 8 to 12 and Comparative Examples 4 and 5 were evaluated.

[0079] For the evaluation, as a polishing apparatus, a CMP apparatus manufactured by CTS Co. was used.

[0080] The measurement results of the polishing rates of the silicon oxide film, the silicon nitride film, and the polysilicon film when the prepared CMP slurry compositions were used are shown in Table 5 below.

TABLE-US-00005 TABLE 5 Removal Rate (=Polishing Rate, Å/min) Selectivity ratio Silicon Silicon (silicon oxide oxide nitride Polysilicon film:silicon nitride film film film film:polysilicon film) Example 8 550 35 100 10.5:1:2.9 Example 9 570 42 450 13.6:1:10.7 Example 10 580 38 50 15.3:1:1.3 Example 11 560 55 95 10.2:1:1.7 Example 12 550 20 105 27.5:1:5.3 Comparative 540 30 575 18:1:19.2 Example 4 Comparative 545 94 90 5.8:1:0.96 Example 5

[0081] Comparing Examples 8 to 12 with Comparative Examples 4 and 5, as shown in Table 5 above, it was confirmed that when the CMP slurry compositions of Examples 8 to 12 were used, the polishing selectivity of each of the silicon oxide film and the polysilicon film to the silicon nitride film increased. Specifically, the polishing selectivity of the silicon oxide film to the silicon nitride film was significantly increased to 1:10 or more.

[0082] In contrast, in the case of Comparative Example 4 in which polyethylene glycol for controlling the removal rate of the polysilicon film was not used, since the removal rate of the polysilicon film was higher than that of the silicon oxide film, there was a problem in that residues of the polysilicon film remained after the CMP process.

[0083] In the case where 5methyl-benzotriazole, which is a heterocyclic compound, is not used as in Comparative Example 5, the removal rate of the silicon nitride film increased, and thus the selectivity of the silicon oxide film and the polysilicon film with respect to the silicon nitride film decreased.

[0084] As described above, when the CMP slurry composition of the present invention was used, it was confirmed that the silicon oxide film and the polysilicon film could be polished with a high polishing selectivity with respect to the silicon nitride film. Therefore, the CMP slurry composition of the present invention can be usually applied to a semiconductor device manufacturing process that requires selective removal of a silicon oxide film and a polysilicon film.