TWI798163B - An alkaline chemical mechanical polishing slurry - Google Patents

Abstract

The invention discloses a kind of alkaline chemical mechanical polishing slurry that can be used for polishing barrier layer.The polishing slurry contains abrasive particles,azole compounds,phosphoric acid,ammonium chloride and hydrogen peroxide solution. The invention uses abrasive particles with an average particle size less than 30nm, so that the polishing rate of a low dielectric material (low-K) is less than the polishing rate of a silicon dioxide (TEOS). Furthermore, fang and defect problems ofa substrate surface were significantly improved after polishing.

Description

A kind of alkaline chemical mechanical polishing fluid

The invention relates to the field of chemical mechanical polishing liquid, in particular to an alkaline chemical mechanical polishing liquid used for barrier layers.

Chemical Mechanical Polishing (CMP), as an essential process in the manufacturing process of semiconductor devices, is the most effective way to planarize the wafer surface. As one of the key elements of CMP, the polishing fluid directly affects the quality of the polished wafer surface, so it has also become an important and indispensable auxiliary material in semiconductor manufacturing. However, when applied to different substrate materials, there will be different requirements for the performance of chemical mechanical polishing fluid. For example, when it is used to polish the barrier layer between silicon dioxide and copper wire, which prevents the diffusion of copper ions to the dielectric layer, the metallic copper above the barrier layer must be removed first, but the polishing solution applied to copper will not be polished. The speed is very fast, and various defects (such as dishing and erosion) will be formed on the substrate. Therefore, when polishing copper, copper CMP is usually required to stop on the barrier layer first, and then change to another A special barrier layer polishing fluid, which can not only remove the barrier layer material (such as tantalum), but also correct dishing and erosion to achieve global planarization. There are two types of commercial barrier polishing fluids, acidic and alkaline, each with its own advantages and disadvantages. For example, the polishing speed of acidic barrier layer polishing liquid on copper is easily adjusted by hydrogen peroxide. Although hydrogen peroxide is stable, the polishing speed on silicon dioxide and TiN is relatively slow; the polishing speed of alkaline barrier layer polishing liquid on copper is not easy to adjust through hydrogen peroxide. In this type of polishing fluid, hydrogen peroxide is unstable, but the polishing speed of silicon dioxide and TiN is relatively fast. In addition, edge-over-erosion (EOE), also known as the "fang" shape, is often encountered in either acid or alkaline polishing conditions. Usually occurs after barrier polishing. At the edge of the bulk copper structure, a trench is formed due to the absence of a dielectric such as silicon dioxide. Occasionally, copper loss due to galvanic corrosion also occurs. The EOE phenomenon will reduce the flatness of the wafer surface. When the conductive layer and the dielectric layer are stacked up layer by layer, it will continue to affect the flatness of the previous layer. As a result, after polishing, there may be copper in the surface depression of each layer. Residues will cause leakage or short circuit, which will affect the stability of semiconductors. Tantalum is a commonly used metal for barrier layers. In the existing polishing technology, US7241725 and US7300480 use imine, hydrazine and guanidine to increase the polishing speed of the barrier layer. US7491252B2 uses guanidine hydrochloride to increase the polishing speed of the barrier layer. US7790618B2 uses imine derivatives and polyethylene glycol sulfate surfactants for the polishing of barrier layers. With the continuous development of technology, Low-K materials are introduced into the semiconductor manufacturing process, and the polishing liquid of the barrier layer, after copper, tantalum, and silicon dioxide, also puts forward higher requirements for the polishing speed of Low-K materials. At present, in the polishing of barrier layers containing Low-K materials, the polishing speed of silicon oxide (TEOS) is required to be greater than or equal to that of Low-K materials. Only in this way can the polishing speed be slowly reduced from the "very fast" at the beginning, and reach a reasonable speed before the polishing stops, and ensure that there is a suitable selection ratio between TEOS/BD/ULK/Cu, so as to realize the global flattened. However, the current alkaline polishing fluid usually has such a disadvantage, that is, the polishing speed of the Low-K material will be significantly greater than the TEOS polishing speed, because the mechanical strength of the Low-K material is weaker than that of TEOS. In order to suppress the high polishing speed of Low-K materials, a polishing speed inhibitor is usually selected to selectively suppress the polishing speed of Low-K materials. This is a very challenging task, because the polishing speed inhibitor usually inhibits the polishing speed of TEOS and Low-K materials at the same time, which will cause the silicon dioxide to not be thrown and the polishing speed to be slow. The more common situation is that although the polishing speed of Low-K materials can be partially suppressed, it is difficult to achieve a polishing speed lower than TEOS. Ultimately, good planarization cannot be achieved. For example, CN101665664A uses quaternary ammonium salt cationic surfactants to suppress the polishing speed of low dielectric materials (such as BD). The cationic quaternary ammonium salts contain long chains above C8, but most quaternary ammonium salt cationic surfactants It will significantly inhibit the polishing speed of silicon dioxide (OXIDE), and will prevent polishing; EP2119353A1 uses poly(methyl vinyl ether) for polishing materials containing Low-K; US2008/0276543A1 uses formamidine, guanidine and polyvinylpyrrolidone (PVP ) for the polishing of the barrier layer. In the above polishing technologies, the problem of edge-over-erosion (EOE) exists to varying degrees. To solve this problem, US20090283715A1 uses polyacrylic acid and its copolymers to suppress excessive edge erosion (EOE). US2005/0208761A1 Suppression of edge over erosion (EOE) with polysaccharides. In the above prior art, the suppression effect of edge over erosion (EOE) is not obvious. In addition, EP0373501B1 also discloses a fine polishing liquid, which uses organic polymers, such as polyvinylpyrrolidone (PVP), to adjust the hydrodynamic properties of the polishing liquid, although it can improve the flatness of the silicon wafer surface and reduce defects. However, this fine polishing liquid is not suitable for metal materials, nor can it solve the problem of excessive edge erosion (EOE). In summary, looking for a polishing solution that can overcome the effect of hydrogen peroxide on the polishing rate, is suitable for barrier materials (including copper, tantalum, silicon dioxide and low dielectric materials), and can prevent "dog teeth" (fang) after polishing. ) phenomenon of polishing liquid, is an urgent problem to be solved in this industry.

In order to solve the above technical problems, the present invention provides an alkaline chemical mechanical polishing fluid for polishing the barrier layer, which adopts abrasive particles with an average particle diameter of less than 30nm to realize oxidation without adding a Low-K material speed inhibitor. The polishing speed of silicon (TEOS) is greater than or equal to that of Low-K materials. This avoids adding additional polishing rate inhibitors for Low-K materials. It avoids the destructive effect of such Low-K material polishing speed inhibitor on the polishing liquid system. It suppresses the occurrence of phenomena such as system instability, abrasive precipitation, damage to copper surface protection, and formation of corrosion scratches. Specifically, the invention discloses an alkaline barrier layer chemical mechanical polishing liquid, which is composed of abrasive particles, azole compounds, phosphoric acid, ammonium chloride, and hydrogen peroxide. Wherein, the average particle size of the abrasive particles is less than 30nm, and the abrasive particles themselves have a silicon dioxide polishing speed greater than that of the low-K material without adding low-K material inhibitors. Wherein, the average particle diameter of the abrasive particles is 15-30nm. Wherein, the concentration of the abrasive particles is 5%-20%. Wherein, the azole compound is benzotriazole (BTA), triazole (TAZ), tolylbenzotriazole (TTA). Wherein, the concentration of the azole compound is 0.01%-0.3%. Wherein, the concentration of the phosphoric acid is 0.05%-0.4%. Wherein, the ammonium chloride concentration is 0-0.03%. Wherein, the hydrogen peroxide concentration is 0.1%-2%. Wherein, the pH value of the abrasive particles is 9-11. After adopting the above technical solution, compared with the existing technology, it has the following beneficial effects: 1. It can be realized that the polishing speed of low-K is lower than that of TEOS (silicon dioxide) without adding surfactant; 1. Significantly improved Eliminate the fang phenomenon after polishing; 2. Significantly reduce the defects caused by polishing.

表2給出了對比拋光液1-4與本發明的拋光液實施例1-6對二氧化矽、低介電材料的拋光速度以及其拋光後產生的腐蝕、犬牙、缺陷現象的比對結果。 拋光條件：所配的拋光液在Mirra上拋光，Fujibo拋光墊，下壓力1.5PSI, 拋光頭/盤轉速：103/97RPM，拋光液流量：140ml/min。   表2對比例1-4與本發明拋光液實施例1-6的拋光效果

其中，TEOS：二氧化矽薄膜，low-k BD：低介電材料薄膜， Erosion：腐蝕，Fang：犬牙，Defect：缺陷。 由圖1可以看出，使用對比例1拋光液拋光後，基材表面產生了尺寸為200Å的fang及170 Å的碟型凹陷，而由圖2可以看出，使用本發明拋光液的實施2，其拋光後，在產生相同尺寸碟型凹陷的基礎上，基材表面產生的fang小於20Å。 另，結合表2中的拋光效果，可以發現：對比例1，2中，未添加low-K 材料抑制劑，其對low-K的拋光速度很快，拋光後會造成很深的Erosion缺蝕，和犬牙（fang）現象；而對比例3，4中，加入了low-K 材料抑制劑以後，low-K的拋光速度會被抑制到小於TEOS（二氧化矽），Erosion會改善，但是犬牙（fang）現象仍然嚴重；而實施例1-6中，使用本發明的配方，可以實現low-K的拋光速度小於TEOS（二氧化矽），同時犬牙（fang）現象和Defect(缺陷)顯著改善。 應當理解的是，本發明所述濃度及符號%均指的是重量(品質)百分濃度。 以上對本發明的具體實施例進行了詳細描述，但其只是作為範例，本發明並不限制於以上描述的具體實施例。對於本領域技術人員而言，任何對本發明進行的等同修改和替代也都在本發明的範疇之中。因此，在不脫離本發明的精神和範圍下所作的均等變換和修改，都應涵蓋在本發明的範圍內。The present invention is further illustrated below by means of examples, but the present invention is not limited to the scope of the examples. Table 1 shows the formulas of Comparative Examples 1-4 and Examples 1-6 of the chemical mechanical polishing fluid of the present invention. According to the formula given in the table, the polishing fluid in the following table can be obtained by mixing evenly. The formula of table 1 comparative example 1-4 and polishing liquid embodiment 1～6 of the present invention

Table 2 shows the comparative results of comparison polishing liquid 1-4 and polishing liquid embodiment 1-6 of the present invention to the polishing speed of silicon dioxide, low dielectric material and the corrosion, houndstooth, defect phenomenon that it produces after polishing . Polishing conditions: the prepared polishing liquid is polished on Mirra, Fujibo polishing pad, downforce 1.5PSI, polishing head/disc speed: 103/97RPM, polishing liquid flow rate: 140ml/min. The polishing effect of table 2 comparative examples 1-4 and polishing liquid embodiment 1-6 of the present invention

Among them, TEOS: silicon dioxide thin film, low-k BD: low dielectric material thin film, Erosion: corrosion, Fang: dog tooth, Defect: defect. As can be seen from Figure 1, after polishing with the polishing solution of Comparative Example 1, the surface of the substrate produced a fang with a size of 200 Å and a dish-shaped depression of 170 Å, and it can be seen from Figure 2 that using the polishing solution of the present invention 2 , after polishing, on the basis of producing dish-shaped depressions of the same size, the fang generated on the surface of the substrate is less than 20Å. In addition, combined with the polishing effect in Table 2, it can be found that in Comparative Examples 1 and 2, no low-K material inhibitor was added, and the polishing speed of low-K was very fast, and deep Erosion corrosion would be caused after polishing , and canine (fang) phenomenon; and in comparative examples 3 and 4, after adding low-K material inhibitor, the polishing speed of low-K will be suppressed to be less than TEOS (silicon dioxide), Erosion will be improved, but the canine The (fang) phenomenon is still serious; while in Examples 1-6, using the formula of the present invention, the polishing speed of low-K can be lower than that of TEOS (silicon dioxide), and the canine (fang) phenomenon and Defect (defect) are significantly improved . It should be understood that the concentration and the symbol % in the present invention both refer to the weight (mass) percentage concentration. The specific embodiments of the present invention have been described in detail above, but they are only examples, and the present invention is not limited to the specific embodiments described above. For those skilled in the art, any equivalent modifications and substitutions to the present invention are also within the scope of the present invention. Therefore, equivalent changes and modifications made without departing from the spirit and scope of the present invention shall fall within the scope of the present invention.

Figure 1 is the fang phenomenon of Comparative Example 1. Figure 2 is the fang phenomenon of Example 2.

Claims (3)

An alkaline barrier chemical mechanical polishing solution, the functional components of which are composed of silicon dioxide abrasive particles, azole compounds, phosphoric acid, ammonium chloride, and hydrogen peroxide, wherein the average particle size of the abrasive particles is 15-30nm; The concentration of the abrasive particles is 5%-20%; the concentration of the azole compound is 0.01%-0.3%; the concentration of the phosphoric acid is 0.05%-0.4%; the concentration of the ammonium chloride is 0.01-0.03%; and The hydrogen peroxide concentration is 0.1%-2%. The basic barrier layer chemical mechanical polishing solution according to claim 1, wherein the azole compounds are benzotriazole (BTA), triazole (TAZ), and tolylbenzotriazole (TTA). The alkaline barrier layer chemical mechanical polishing solution according to claim 1, wherein the pH value of the alkaline barrier layer chemical mechanical polishing solution is 9-11.

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