KR100351442B1 - Abrasive for shallow trench isolation chemical mechanical polishing and polishing method using it - Google Patents

Abstract

The present invention relates to an abrasive used in the STI CMP process and a polishing method used as a planarization process in the device separation process, and to mixing Corundum-B, S202 (SHOWA DENKO Co.) and pure water, which are additive components of Corundum (RODEL Co.). The purpose of the present invention is to provide a polishing agent and a method for polishing under optimized polishing conditions. According to the present invention, both the scratch problem occurring when using the existing corundum and the bad polishing uniformity caused by the low polishing selectivity occurring when using S202 and the problem of low process margin are solved. By solving the problems of low polishing selectivity and scratch induction, which were the biggest problems of STI CMP, it is possible to reduce the process step because STI CMP can be obtained at once without complex process such as reverse etching. In addition, process margins are widening.

Description

ST-CPM abrasive and polishing method using the same {ABRASIVE FOR SHALLOW TRENCH ISOLATION CHEMICAL MECHANICAL POLISHING AND POLISHING METHOD USING IT}

The present invention relates to an abrasive and a polishing method used in the STI CMP (Shallow Trench Isolation Chemical Mechanical Polishing) used as a planarization process in the device isolation process, and Corundum-B and S202 (SHOWA DENKO), which are additive components of Corundum (RODEL Co.). The present invention relates to a polishing method having a low defect incidence rate and a high polishing selection ratio and a wide processing margin by applying an abrasive produced by mixing Co.) and pure water (DIW) and optimized polishing conditions.

The biggest feature of the STI CMP polishing liquid is the high polishing selectivity between the oxide film and the nitride film. This is because when the polishing liquid having a high polishing selectivity is used, not only the polishing uniformity is reliably guaranteed, but also an additional process such as reverse etching to ensure the polishing uniformity is unnecessary, and a very wide process margin is also secured. Therefore, the polishing liquid supplier is developing STI CMP polishing liquid with high polishing selectivity, and some are pursuing commercialization.

Among them, RODEL's Corundum and SHOWA DENKO's GPL-C S202 (hereinafter referred to as S202) are the most likely polishing liquids. These polishing liquids have advantages and disadvantages, respectively.

First, RODEL's Corundum has a high polishing selectivity (flat polishing selectivity> 100), while it is very vulnerable in terms of defects such as large scratches. On the other hand, SHOWA DENKO's S202 has excellent defects such as scratches, compared to Corundum, but its polishing selectivity is low from 30 to 80, and it is unstable depending on the surface of the polishing pad. Therefore, in consideration of the margin of the polishing process, the polishing uniformity is sharply worsened when a little overpolishing enters.

In summary, Corumdum causes about 1000 scratches based on 8-inch wafers, but the polishing uniformity is very favorable and wider in process margin than S202 due to the high selectivity, but S202 shows the opposite trend. .

In the present invention, in order to solve the above problems, in the STI CMP (Chemical Mechanical Polishing) process, which is a planarization process of STI (Shallow Tranch Isolation), which is one of the separation processes of semiconductor devices, a novel defect having a low defect density and a high polishing selectivity It is intended to provide a polishing liquid for STI CMP and a polishing method using such polishing liquid.

1 is a graph showing the thickness of the nitride film remaining according to the degree of overpolishing using the polishing liquid according to the present invention,

2 is a graph showing the scratch occurrence density when using the polishing liquid according to the present invention and when using the conventional polishing liquid.

The present invention to achieve the above technical problem (a) S2O2 stock solution; And (b) STI-CMP abrasive for a semiconductor manufacturing process comprising a mixed solution of Corundum B and pure water, wherein (a) S2O2 stock solution (SHOWA DENKO Co.) and (b) Corundum B (RODEL Co.) and pure water. The mixed solution of is contained in the abrasive in a volume ratio of 1:10, (b) the mixed solution of Corundum B and pure water is characterized by consisting of 10-50% by volume Corundum B and 50-90% by volume pure water Provided are STI-CMP abrasives.

The present invention also provides a polishing method, characterized in that the polishing using the abrasive.

In the polishing method according to the present invention, the pressure is 2 to 4 psi and the rotation speed of the polishing plate is preferably 40 to 70 rpm.

In addition, the pad conditioning in the polishing method according to the present invention is preferably carried out in an ex-situ state.

The pad conditioning is used to refresh the surface of the polishing pad. The in-situ conditioning is only about 2/3 of the polishing rate than the ex-situ condition. Because you can not. It is a characteristic of polishing liquids that use ceria as an abrasive to ex-situ conditioning with higher polishing rates. Therefore, it is preferable that the conditioning in the case of using ceria as the abrasive proceeds mostly in an ex-situ state.

Corundum Abrasive Liquid is composed of Corundum A and Corundum B. Corundum A contains mainly abrasives, Corundum B contains mainly organic components that increase the polishing selectivity. Corundum A and Corundum B have a volume ratio of about 1: 5. It is mixed. In addition, S202 has a solid content of 10% by weight, and contains organic components that increase the polishing selectivity.

When using S202, S202 is mixed with pure water in a volume ratio of about 1: 10 and diluted to about 1 weight percent of total solids.

As mentioned above, in the abrasive according to the present invention, the ratio of the mixed solution of (a) S2O2 stock solution and (b) Corundum B and pure water is (a) S2O2 stock solution: (b) a mixed solution of Corundum B and pure water. Preferably, the ratio is 1:10 by volume, and the ratio of Corundum B in the mixed solution of (b) Corundum B and pure water is preferably 10-50% by volume. That is, even if the mixing ratio of Corundum B and pure water is about 1: 9, sufficient polishing selectivity, low defect density and process margin can be obtained. However, when the ratio is smaller than 5: 5, that is, If the ratio is less than 50% by volume, the middle portion of the wafer is not polished, and the polishing selectivity may be lowered.

As described above, the ratio of S202 Stock Solution: Corundum B: Pure Water is based on the experiments of various combinations of S202 Stock Solution: Corundum B: Pure Water in order to obtain high polishing ratio and low defect density. It is supported by the experimental example.

Experiment 1:

The polishing rate and the polishing selectivity were determined using a S202 stock solution (10% weight): Corundum B mixing ratio of 1: 10. Polishing conditions were pressure 3psi, polishing spin speed 50rpm, wafer carrier rotation speed 50rpm, it was carried out under the condition of ex-situ method. The results are shown in Table 1 below.

Polishing Speed (Å / min) Polishing nonuniformity (%) PETEOS oxide 255 35.7 LPCVD Nitride 34 Polishing selection ratio 7.6

As a result of the experiment, we found very low polishing speed and extreme unevenness of the center of the wafer. This phenomenon is probably due to the organic component of Corundum B. The organic component of Corundum B has a property of complexing both oxide film and nitride film. In particular, since the compounding tendency of the nitride film is strong, the nitride film shows a very slow polishing rate compared to the oxide film and is not polished. (See USP 5738800, 5476606)

Therefore, pure water was added to weaken the organic properties of Corundum B.

Experiment 2:

S202 Stock solution (10% weight): Corundum B: The mixing ratio of pure water was 1: 5: 5 volume ratio and the polishing rate and polishing selectivity were calculated. Polishing conditions were pressure 3psi, polishing spin speed 50rpm, wafer carrier rotation speed 50rpm, it was carried out under the condition of ex-situ method. The results are shown in Table 2 below.

Polishing Speed (Å / min) Polishing nonuniformity (%) PETEOS oxide 1208 7.6 LPCVD Nitride 35 Polishing selection ratio 34

As a result of the experiment, as the pure water was added, the polishing rate of the oxide film was rapidly increased and the polishing uniformity was found to be very good. However, the polishing selectivity of flat wafers was similar to that of S202 compared to that of Corundum over 100. This experiment was carried out twice. In the second experiment, the polishing selectivity was about 22, so it was not possible to obtain the advantage in the polishing selectivity by mixing the two polishing liquids.

However, after polishing the pattern wafer rather than the flat wafer, the thickness of the nitride film remaining after polishing was very uniform, as was polished with corundum. This phenomenon is not seen in S202 with similar polishing selectivity, and it is assumed that it is influenced by Corundum B, an organic component in the polishing process of pattern wafer.

In particular, the zeta potential of the organic component of Corundum B is estimated to be due to the zeta potential. This is because the organic component of Corundum B is oriented toward the nitride film and the surface of the nitride film is compounded, thereby suppressing the polishing of the nitride film and the oxide film being continuously polished.

Experiment 3:

In addition, in order to obtain the minimum amount required to obtain a good polishing selection ratio S202 Stock solution (10% by weight): Corundum B: The pattern wafer was ground by mixing the ratio of pure water to 1: 3: 7 and 1: 1: 9. It was confirmed that the polishing uniformity was similar to that of the experiment with a mixing ratio of 5: 5.

1 shows the thickness of the nitride film remaining according to the degree of overpolishing using the polishing liquid according to the present invention. In FIG. 1, the X axis represents the degree of overpolishing with CMP, and the Y axis represents the thickness of the nitride film remaining after polishing. As shown in the following drawings, the overpolishing was performed up to 30%, but the nitride film was not polished and the thickness was maintained as it is.

In the case of proceeding to the conventional S202, in the case of 30% over-polishing, the nitride film of 900 막 remains and the thickness of the remaining nitride film is about 300Å, whereas the polishing uniformity of the present invention is almost the same as that of Corundum. .

As a result, the margin of polishing is widened and the process margin is also widened. This phenomenon is due to the high polishing selectivity.

Experiment 4:

S202 Stock solution: Corundum B: Polishing the patterned wafer with a polishing liquid with a mixing ratio of 1: 1: 9 (hereinafter abbreviated as MSC119 as abbreviation for Mixture of S202 and Corundum) and inspecting defects using KLA2132 equipment. Was done.

2 shows the density of scratches generated when MSC119 was used as compared to the case of Corundum and S202. In FIG. 2, Y-axis is the density of scratches found per unit cm ^2, and S202 and MSC119 both exhibit low density scratches compared to Corundum, and there is almost no difference in scratch density between S202 and MSC119. This phenomenon appears to be caused by the size of the particles and the shape of the particles (Ceria) particles included in the abrasive, presumably because MSC119 and S202 using the same S202 particles.

Based on the experimental results, it was possible to obtain high polishing selectivity and low defect density by mixing S202 stock: Corundum B: pure water in an appropriate amount.

The polishing process as described above can be applied to other CMP processes, such as copper wiring planarization or tungsten plug planarization process, in which polishing selectivity is important. In particular, in the case of copper wiring, the polishing uniformity of oxide film is increased by increasing the polishing selectivity of copper and oxide film. While increasing the effect of protecting the copper wiring.

As described above, according to the present invention, the effects of solving both the scratch problem caused by using the conventional Corundum B and the problem of poor polishing uniformity and low process margin due to the low polishing selectivity caused by using S202 are solved. Indicates.

In addition, by solving the problems of low polishing selectivity and scratch induction, which are the biggest problems of the existing STI CMP, it is possible to achieve good polishing uniformity even if the STI CMP is performed at once without complicated process such as reverse etching. Not only that, but also the process margin is widened, so it can be easily applied to mass production system.

Claims (6)

(a) an S 2 O 2 stock solution; And (b) STI-CMP abrasive for semiconductor manufacturing process comprising a mixed solution of Corundum B and pure water, The (a) S2O2 stock solution and (b) a mixed solution of Corundum B and pure water are included in the abrasive in a volume ratio of 1: 10, and (b) the mixed solution of Corundum B and pure water is 10-50 volume% of Corundum B And 50-90% by volume pure water. delete delete The STI-CMP polishing method in the semiconductor manufacturing process, characterized by using the abrasive according to claim 1. 5. The STI-CMP polishing method according to claim 4, wherein the pressure is 2-4 psi and the rotation speed of the polishing plate is 40-70 rpm. The STI-CMP polishing method according to claim 4, wherein the polishing is performed under an ex-situ.