TWI881938B - Chemical mechanical polishing slurry - Google Patents

Abstract

The present invention provides a chemical mechanical polishing slurry, wherein comprising cerium oxide abrasives, oligosaccharide and pH modifier. The invention also provides a use of the chemical mechanical polishing slurry on polishing the surface of the silica media. Using the chemical mechanical polishing slurry of the present, can reduce the defects of the surface of the substrate, and significantly raise the polishing rate of the cerium oxide abrasives to the silica media.

Description

Chemical mechanical polishing liquid and its uses

The present invention relates to the field of chemical mechanical polishing liquid, and in particular to a chemical mechanical polishing liquid containing β-cyclodextrin molecules.

Basalt oxide is an important abrasive for CMP polishing liquid. Compared with traditional silica sol abrasives, due to its more efficient polishing properties, it has been widely used in STI and LID CMP polishing liquid. At present, the basalt oxide abrasives used for CMP polishing are mainly divided into two types: one is the basalt oxide abrasive dispersion prepared by ball milling of traditional high-temperature calcined synthesized basalt oxide powder; the other is the sol-type nano-basalt oxide abrasive prepared by hydrothermal synthesis. The two types of bismuth oxide abrasives have different polishing properties: the bismuth oxide abrasive synthesized by traditional high temperature calcination can improve its polishing rate on the silicon dioxide dielectric layer by adding compounds such as picolinic acid (see reference: Carter et al., Electrochemical and Solid-State Letter (vol 8(8), page G218-G221, year 2005); while for sol-type bismuth oxide, the addition of picolinic acid not only fails to improve its polishing rate on the silicon dioxide dielectric layer, but also inhibits the polishing activity of bismuth oxide. (See Case 1). The literature mentions that different bismuth oxide preparation methods have different effects on polishing activity and chemical compounds (see reference: Srinivasan et al., ECS Journal of Solid State Science and Technology,4(11)P5029-P5039(2015))

However, as the technology nodes of integrated circuits develop towards smaller sizes, the process has put forward lower polishing defect requirements for the CMP polishing process. The bismuth oxide abrasive synthesized by the traditional high-temperature calcination method has multi-angular particles, and micro scratches are inevitably generated during the CMP polishing process, so it is difficult to meet the CMP polishing requirements of advanced processes. Sol-type bismuth oxide abrasives have nearly round particle morphology and good CMP polishing application prospects, and are receiving more and more attention. Therefore, it is necessary to provide a chemical mechanical polishing liquid formula using sol-type bismuth oxide as an abrasive, which can not only maintain the lower polishing defect characteristics of the existing sol-type bismuth oxide polishing liquid, but also achieve the high polishing rate of silicon dioxide of the bismuth oxide abrasive synthesized by the traditional high-temperature calcination method.

In order to solve the above-mentioned problem of polishing rate, the present invention provides a chemical mechanical polishing liquid containing β-cyclodextrin molecules, which uses vanadium oxide as an abrasive, which can ensure lower polishing defects and significantly improve the polishing rate of silicon dioxide dielectric materials.

The chemical mechanical polishing solution contains a vanadium oxide abrasive, a β-cyclodextrin molecule and a pH adjuster.

Preferably, the indium oxide abrasive comprises a sol-type indium oxide abrasive.

Preferably, the particle size of the diatomite abrasive is 30-90nm.

Preferably, the concentration of the diatomite abrasive is 0.05wt%-2wt% by mass.

Preferably, the concentration of the β-cyclodextrin molecules is 0.005wt%-2wt%, preferably 0.005wt-0.1wt%.

Preferably, the pH value of the chemical mechanical polishing solution is 3.5-5.5.

The present invention also discloses the application of a chemical mechanical polishing liquid in polishing the surface of silicon dioxide medium.

Compared with the prior art, the positive improvement of the present invention is that: By adding β-cyclodextrin molecules to the chemical mechanical polishing solution, it can ensure lower polishing defects and significantly improve the polishing rate of tetraethoxysilane (TEOS) by the bismuth oxide abrasive.

The particle size mentioned in the present invention is based on electron microscopy. For the same particle, the results of electron microscopy and light scattering (DLS) are different, see the following table:

The data is quoted from the literature: Pandija et al, "Effect of Ceria Size and Concentration in Shallow Trench Isolation (STI) Chemical Mechanical Polishing (CMP)" in International Conference on Planarization/CMP Technology. October 25-27,2007 Dresden, VDE VERLAG GMBH． Berlin-Offenbach

The advantages of the present invention are further described below through specific embodiments, but the scope of protection of the present invention is not limited to the following embodiments.

Embodiment 1

Table 1 shows the effect of adding picolinic acid, ionic electrolyte and non-ionic electrolyte to the chemical mechanical polishing solution on the polishing rate of silicon dioxide. Among them, the concentration of picolinic acid is 0.01wt%-0.20wt%; the ionic electrolytes are potassium nitrate (KNO ₃ ), potassium chloride (KCl), potassium acetate (KAc), tetramethylammonium acetate (TMAAc), tetramethylammonium butyrate (TBAAc), and the concentration is 0.10wt%; the non-ionic electrolytes are benzotriazole (BTA), triazole (TAZ), polyethylene glycol (PEG), ethylene glycol (Ethylene glycol), mannitol (Mannitol), sorbitol (Sorbitol) and sucrose (Sucrose) and β-cyclodextrin. The corresponding sol-type konium oxide concentration is 1wt%, the average particle size is 60nm, and the pH is adjusted to 4.5 with potassium hydroxide (KOH) or nitric acid (HNO ₃ ). The light liquid polishing performance is evaluated by the polishing removal rate of the corresponding TEOS blank wafer. The Mirra polishing machine is used for polishing test. The corresponding polishing conditions include: IC1010 polishing pad, the base and polishing head speeds are 93rpm and 87rpm respectively, the pressure is 3psi, the polishing liquid flow rate is 150mL/min, and the polishing time is 60 seconds. The corresponding TEOS polishing rate of the comparative example is 5800Å/min.

As shown in Table 1, it can be seen from comparative examples 1-6 that the effect of the addition of picolinic acid on the polishing activity of tantalum oxide increases with the increase of its concentration. Compared with the blank comparative example, when the concentration of the added picolinic acid is 0.2wt%, the corresponding TEOS polishing rate decreases by 50% to only 2900Å/min.

In addition, it can be seen from Comparative Example 1 and Comparative Examples 7-11 that the addition of ionic electrolytes also has a significant inhibitory effect on the polishing rate of sol-type tin oxide. In particular, when potassium chloride (KCl) ionic electrolyte is added to the polishing solution, the polishing rate of TEOS by the polishing solution is inhibited by 54% compared with the blank comparative example, and the TEOS polishing rate is only 46% of the comparative example.

From Comparative Example 1, Comparative Examples 12-23 and Examples, it can be seen that the addition of non-ionic electrolytes will also have a certain inhibitory effect on the polishing rate of sol-type indium oxide, but its influence is much smaller than that of ionic electrolytes. However, as an exception, β-cyclodextrin molecules as non-electrolytes can further promote the polishing rate of sol-type indium oxide. When 0.01wt% of β-cyclodextrin is added to the polishing solution, the polishing rate of sol-type indium oxide on TEOS increases by 2%.

Embodiment 2

Table 2 is a further optimization study on the effect of adjusting the amount of β-cyclodextrin added and the molecular weight on the polishing rate of sol-onium oxide. By adjusting the amount of β-cyclodextrin added and the molecular weight in the formula system, the improvement level of β-cyclodextrin on the polishing rate of sol-onium oxide was further optimized. The polishing performance of the polishing liquid was evaluated by the polishing removal rate of the corresponding TEOS blank wafer. The Mirra polishing machine was used for the polishing test. The corresponding polishing conditions included: IC1010 polishing pad, the base and polishing head speeds were 93rpm and 87rpm respectively, the pressure was 3psi, the polishing liquid flow rate was 150mL/min, and the polishing time was 60 seconds. Table 3 shows the formulation of the polishing solution, which corresponds to a sol-type tin oxide concentration of 1wt%, an average particle size of 60nm, and a pH of 4.5 adjusted with potassium hydroxide (KOH) or nitric acid (HNO ₃ ). The formulation without adding an ionic electrolyte corresponds to a TEOS polishing rate of 5800Å/min.

As shown in Table 2, it can be seen from the comparative example and examples 1-6 that when the concentration of added β-cyclodextrin is from 0.001-2wt%, the polishing rate of TEOS by the sol-type konium oxide abrasive in the polishing solution is improved; in particular, when the content of β-cyclodextrin is 0.005wt%, the improved TEOS polishing rate is most significant, which is 4% higher than the polishing solution without addition. It can be seen from example 7 that when the content of β-cyclodextrin reaches 0.500wt%, the polishing rate of TEOS by the sol-type konium oxide abrasive in the polishing solution begins to decrease, which is 2% higher than the polishing solution without addition.

Implementation Example 3

Table 3 shows the effect of adding β-cyclodextrin to the polishing solution on the polishing rate of TEOS under different conditions of bismuth oxide concentration, particle size and pH value. As shown in Table 3, when the particle size of bismuth oxide is 30-90nm, the concentration of bismuth oxide is 0.05-2wt%, and the pH value of the polishing solution is 3.5-5.5, adding a certain amount of β-cyclodextrin can significantly increase the polishing rate of the polishing solution for TEOS. The addition of β-cyclodextrin can promote the polishing performance of bismuth oxide to a certain extent under different pH and solid content of bismuth oxide abrasive.

In summary, compared with the addition of picolinic acid, ionic electrolytes and other non-ionic electrolytes, when β-cyclodextrin molecules are added to the chemical mechanical polishing solution with sol-type bismuth oxide as abrasive, it not only does not inhibit the polishing rate of the sol-type bismuth oxide abrasive, but can increase its polishing rate for silicon dioxide. The content of the β-cyclodextrin molecules is further optimized. It can be seen that when the content of β-cyclodextrin in the polishing solution is 0.005wt%, the sol-type bismuth oxide abrasive can achieve the optimal polishing rate for silicon dioxide, which is 4% higher than the polishing solution without addition. Therefore, the chemical mechanical polishing liquid provided by the present invention uses sol-type konium oxide as an abrasive. After adding β-cyclodextrin molecules, it can be used to significantly improve the polishing rate of sol-type konium oxide abrasive on silicon dioxide dielectric materials, providing an optimized solution to the polishing rate problem of sol-type konium oxide.

Claims (2)

A chemical mechanical polishing liquid, comprising a bismuth oxide abrasive, oligosaccharides and a pH regulator; wherein the oligosaccharides are selected from β-cyclodextrin; the bismuth oxide abrasive comprises a sol-type bismuth oxide abrasive; the particle size of the bismuth oxide abrasive is 30-90 nm; the pH value of the chemical mechanical polishing liquid is 3.5-4.5; the concentration of the bismuth oxide abrasive is 0.05wt%-2wt%; and the concentration of the β-cyclodextrin molecules is 0.005wt%-0.5wt%. A use of the chemical mechanical polishing solution as described in claim 1 in polishing the surface of a silicon dioxide medium.