JP2006066851A - Chemical machine polishing composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polishing composition, especially a polishing composition for CMP wherein high polishing speed is attained in spite of not needing combination of polish abrasive grains, and faults such as dishing can be reduce though bad influence of an anticorrosive is excepted, and to provide a method for polishing copper or a copper alloy wiring board by especially applying the polishing composition for CMP to CMP of copper or the copper alloy wiring board. <P>SOLUTION: In the polishing composition, a water medium, an oxidant, a polish accelerator which has both polish accelerating nature and corrosion proof functionality, and a friction reduction agent if it is requested are contained, a polish abrasive grain is not blended, and furthermore, the anticorrosive is not necessarily blended. A polishing method of a metal (copper) surface which uses the polishing composition is also provided. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a polishing composition used for polishing semiconductors, photomasks, substrates and heads for various memory hard disks, and various industrial members, and particularly for polishing that is optimal for surface planarization of device wafers in the semiconductor industry and the like. It relates to a composition. More particularly, the present invention relates to a polishing composition suitable for chemical mechanical polishing of a copper or copper alloy wiring board. Furthermore, this invention relates to the grinding | polishing method of the copper wiring board especially using the said polishing composition.

  In recent years, semiconductors have been reduced in size and performance, and the key processes in this advance are the integration, miniaturization, and multilayering of wiring. In the process of manufacturing these semiconductors, a chemical mechanical polishing (CMP) process has attracted attention because it can flatten the surface of a semiconductor wiring substrate, and its practical application has progressed as an essential technology for semiconductor manufacturing, and the CMP process is a very important process. It has become. Furthermore, as a metal wiring material, copper or copper alloy wiring, which is a low resistance (high dielectric constant) material, is used in place of conventional aluminum alloy and tungsten in order to realize miniaturization and high speed of wiring. . As a method of forming copper or copper alloy wiring on the substrate, a copper thin film is deposited on the insulating film in which the groove is formed via a barrier metal or the like, and the copper thin film other than the portion embedded in the groove is CMP. In general, a so-called damascene method is employed in which a buried wiring is formed by removing the substrate by the above method.

  Chemical mechanical polishing compositions used in CMP for metal wiring (CMP slurry, hereinafter referred to as polishing liquid) are organic as polishing abrasives and polishing accelerators such as silica, alumina and cerium oxide in order to improve the polishing rate. Acids and inorganic acids are generally used. It is also common to add hydrogen peroxide water or the like as an oxidizing agent during wafer polishing.

  Conventionally, forming a complex with an organic acid and copper, and developing the polishing rate by removing the complex with the blended abrasive grains, those expressing the polishing rate by compounding a substance that makes copper water-soluble, etc. Several methods have already been shown.

  On the other hand, for copper wiring, a combination with a low dielectric constant interlayer insulating film called Low-k or Ultra Low-k (hereinafter referred to as UL-k) has become mainstream, but due to its low mechanical strength, The problem of film destruction and film peeling has become apparent.

In order to cope with this problem, it is useful and essential to reduce damage to the film due to polishing at a low polishing pressure and to reduce friction between the wafer and the pad during polishing.
Polishing at about 10 kPa in the case of Low-k and 7 kPa or less in UL-k is said to be essential. However, there is a problem that the polishing rate is reduced by polishing at a low pressure. A decrease in the polishing rate leads to an increase in the polishing time, that is, a decrease in productivity. However, in order to improve the polishing rate, it is necessary to add a large amount of polishing accelerator and to set a high polishing abrasive concentration. A large amount of polishing accelerator is compounded by dishing mainly due to chemical etching of the wiring material (the central part of the surface of the metal wiring embedded in the groove formed in the insulating film is removed more than the peripheral part and is recessed. Phenomenon: The progress of FIG. 2), contamination of the surface of the wiring metal after polishing and the process environment, excessive cleaning and treatment of a large amount of waste liquid are required.
In order to suppress dishing due to chemical etching, it is useful to add a corrosion inhibitor. However, containing an excessive anticorrosive agent causes a decrease in polishing rate and a deterioration in polishing uniformity on the wafer polishing surface. Further, it is known that the cleaning performance after polishing is adversely affected.

  On the other hand, excessive addition of abrasive grains deteriorates dishing and erosion (the phenomenon that the insulating film in the part where the wirings are densely arranged becomes thin: FIG. 3), scratch (on the metal film or insulating film after polishing is completed). Increase in the number of scratches generated on the wafer, an increase in friction between the wafer and the pad during polishing, and an increase in labor for waste liquid treatment. Furthermore, the barrier metal is easily polished and removed by the mechanical action of the abrasive grains, and the underlying insulating film is easily exposed. In that case, there is a drawback that the removed wiring metal is likely to diffuse into the insulating film, and in the case of copper as the main wiring material, it is easier to diffuse into the insulating film than other wiring materials, and defects such as leakage are caused. Prone to occur.

  Therefore, instead of relying solely on conventional mechanical elements (polishing pressure and abrasive grains), we are moving toward increasing the chemical effect, and one of the answers is that "abrasive free" Type "polishing liquid. Abrasive-free type polishing liquids include several methods such as those that develop polishing speed by compounding substances that make copper water-soluble, and those that improve polishing performance by the synergistic effect of organic acid and phosphoric acid. Has already been shown, but there are many challenges.

  In the prior art, in order to improve the polishing rate, it has been proposed to use an organic acid or an inorganic acid, but no significant improvement in the polishing rate when used alone or in combination has been reported. . On the other hand, in order to obtain a high polishing rate using these materials, it is essential to mix a material having high etching properties with respect to the abrasive grains or the wiring metal. The composition of abrasive grains has the above-mentioned problems. On the other hand, the polishing rate is improved by increasing the etching property to the wiring metal, but the performance as a device is not sufficiently exhibited due to the decrease in the wiring capacity due to the wiring metal corrosion. There is an important issue.

  In addition, a method is disclosed in which 2-quinolinecarboxylic acid is used to form a copper complex that is hardly soluble in water and mechanically weaker than copper to achieve both polishing speed and dishing (for example, Patent Documents). 1). However, in this case, in order to remove the copper complex, the inclusion of abrasive grains is essential, and the above problem cannot be solved.

  Furthermore, by adding an organic acid such as citric acid and an anti-corrosion agent such as benzotriazole to an oxidizing agent such as hydrogen peroxide, the concentration of abrasive grains can be kept to a very small amount or polishing without using abrasive grains. Although liquids have also been proposed (see, for example, Patent Document 2), excessive water-solubilization of copper leads to dishing, and the addition of an anticorrosive is essential, while suppressing the water-solubilization of copper is a polishing rate. Will also be suppressed.

  On the other hand, a polishing liquid that exhibits a high polishing rate without containing polishing and abrasive grains by using phosphoric acid and organic acid in combination is also shown (for example, see Patent Document 3 and Patent Document 4). Is mandatory.

  Japanese Patent No. 3192968   Japanese Patent No. 3371775   JP 2002-50595 A   JP 2003-27304 A

  Therefore, the problem of the present invention is to achieve a high polishing rate despite not requiring the blending of abrasive grains that cause the problem, and to eliminate defects such as dishing while excluding the adverse effects of the anticorrosive agent. An object of the present invention is to provide a polishing composition, particularly a CMP polishing composition, capable of reducing the above-mentioned. Furthermore, another object of the present invention is to provide a method for polishing a copper or copper alloy wiring board by applying these polishing compositions for CMP, particularly to CMP of a copper or copper alloy wiring board.

  The present inventors have used the means that the anticorrosive agent that contributes to the above-mentioned problems as much as possible or not at all, eliminates the adverse effects of the anticorrosive agent, and polishing performance, particularly polishing performance under low polishing pressure Tried to maintain.

  Furthermore, we focused on the development of a polishing liquid that can exhibit polishing performance without blending abrasive grains. Therefore, without the need for abrasive grains, the reaction product of the formed polishing accelerator and copper can be easily removed only by friction with the pad, while the formed reaction product is water-insoluble and the wiring recess that the pad does not reach So, we focused on substances that function as protective films. As a result of intensive studies, we confirmed a substance possessing contradictory functions, and by using this substance, the abrasive grains and the anticorrosive agent are not necessarily required, and a high polishing rate and dishing can be suppressed. The invention has been completed.

That is, the present invention relates to the following (1) to (9).
(1) A polishing composition containing a polishing accelerator having a polishing acceleration property and anticorrosion function for metals, an aqueous medium and an oxidizing agent, and containing no abrasive grains.
(2) Further, the polishing composition does not contain an anticorrosive agent.
(3) Preferably, the anticorrosive is a triazole compound and / or a derivative thereof.
(4) In a preferred embodiment, the polishing accelerator is a polishing composition comprising a carboxylic acid and / or a salt thereof.
(5) In a more preferred embodiment, the carboxylic acid and / or salt thereof is a polishing composition which is oxalic acid.
(6) Still further, the polishing composition may contain a friction reducing agent.
(7) Preferably, the abrasive friction reducing agent is a fatty acid and / or an amine salt of a fatty acid.
(8) Moreover, this invention is a metal grinding | polishing method using the polishing composition as described in said (1)-(7).
(9) Preferably, the metal has copper or a copper alloy as a main component.

According to the present invention, first, by using a polishing accelerator having both high polishing performance and anticorrosion function, it is not always necessary to add an anticorrosive agent, and a high polishing rate can be maintained.
In the future, a process using UL-k, which is expected to be developed, can be used under a low polishing pressure, thereby reducing damage to the insulating film and improving productivity. Further, by using this polishing accelerator, it is not necessary to mix abrasive grains, and dishing, erosion, and friction between the pad and the wafer during polishing, which are adverse effects of the abrasive grains, can be reduced.

  On the other hand, since the polishing rate for the barrier metal can be kept low, an extremely excellent wiring material / barrier metal polishing selection ratio can be obtained. Furthermore, embedding of abrasive grains in the wiring metal and generation of scratches can be reduced, and the cleaning process can be simplified while improving the device production efficiency. Further, since clogging of the polishing pad can be reduced, it is possible to reduce the subsequent influence due to the remaining abrasive grains on the pad surface. In addition, the pad life can be extended by reducing the number of times of conditioning and time, and a large cost reduction can be achieved.

  The polishing composition of the present invention has an extremely low polishing rate for tantalum, tantalum nitride, titanium, titanium nitride, tungsten, tungsten nitride and the like, which are mainly used as a barrier metal, and allows the barrier metal to exist stably. In addition to suppressing the diffusion of the removed wiring metal into the insulating film, it can greatly contribute to the easy detection of the polishing end point. In addition, the incorporation of a friction reducing agent makes it possible to reduce the pad-wafer friction during polishing with the polishing liquid itself, and can contribute greatly to future device and process development, along with high polishing performance at low pressure. .

  The polishing composition of the present invention contains an aqueous medium, an oxidizing agent, a polishing accelerator having both polishing acceleration and anticorrosion function, and optionally a friction reducing agent, but does not contain abrasive grains. Furthermore, the anticorrosive agent is not necessarily blended. Even if the polishing accelerator does not contain abrasive grains, the reaction product of the formed polishing accelerator and copper can be easily removed only by friction with the pad, while the formed reaction product is water-insoluble and the pad is insoluble. For wiring recesses that cannot be reached, a substance that functions as a protective film is required. The polishing accelerator used in the present invention is preferably a component composed of carboxylic acid and / or a salt thereof.

  However, an oxyacid containing a hydroxyl group has a high etching property with respect to copper, and is not suitable as a polishing accelerator in terms of dishing. In order to exhibit a high polishing rate, a substance containing two or more carboxyl groups is desirable. However, when the number is three or more, etching with respect to copper increases, so the number of carboxyl groups is preferably two.

  However, it has been found that inclusion of other functional groups, such as amino groups, suppresses the copper polishing rate, and materials not containing these are suitable. In view of the above, the component consisting of carboxylic acid and / or its salt includes oxalic acid, malonic acid and / or its derivative, succinic acid / or its derivative, fumaric acid, maleic acid / or its derivative, glutaric acid / or Preferred are components selected from derivatives thereof, adipic acid / or derivatives thereof, phthalic acid and / or derivatives thereof, and mixtures thereof. Of these, oxalic acid is most preferred.

  The content is selected depending on the required polishing performance, but it is preferably 0.5 to 10 parts by weight with respect to 1000 parts of the aqueous medium, and both the expression of the polishing rate required in this range and the suppression of dishing are compatible. Can do. More preferably, it is 2 to 6 parts by weight.

  When the content of the polishing accelerator (typically oxalic acid) is high, the formation of a reaction product with metal (typically copper and copper alloy) is promoted, and the balance between the formation of the reaction product and the removal by the pad is lost. In some cases, reactants that could not be removed remain and accumulate, so that they remain as a strong protective film, and the polishing performance may deteriorate due to inhibition of the reaction between the polishing accelerator and copper. . In addition, it must be noted that if the reaction is not sufficiently performed, the formation of a reaction product as a protective film is reduced as the polishing rate is lowered, and the original performance is not exhibited. Therefore, it is important to set the optimum polishing accelerator (typically oxalic acid) content according to the polishing conditions.

  In Japanese Patent No. 3192968, by using 2-quinolinecarboxylic acid, copper etching suppression and polishing rate improvement are shown, but in this case, it is essential to blend abrasive grains, It has no effect.

  In addition, there is Patent No. 3371775 as a polishing grain-free type polishing liquid using an organic acid, but in this case, polishing performance is expressed by making copper water-soluble, and containing an anticorrosive agent This is clearly different from the object of the present invention.

  As an abrasive-free type polishing liquid using oxalic acid, an application has been filed as an invention relating to the present inventors (Japanese Patent Laid-Open No. 2003-273044). However, the present invention aims to improve the polishing performance by using phosphoric acid and oxalic acid in combination, and is premised on containing an anticorrosive. The formation of a reaction product as a self-protecting film possessed by oxalic acid is different from the present invention which does not necessarily assume the inclusion of an anticorrosive agent.

Furthermore, fatty acid and / or amine salt of fatty acid used for a general lubricant can be used as a polishing friction reducing agent. Preferably, a fatty acid having 6 to 18 carbon atoms, more preferably 8 to 12 carbon atoms is desirable. The content of the fatty acid is 0.1 to 200 parts, more preferably 0.5 to 100 parts, with respect to 1000 parts of the aqueous medium.
Depending on the type and concentration of the fatty acid, it may not be dissolved in the polishing liquid. In this case, a salt with an amine or the like is formed to facilitate dissolution in the polishing liquid. Addition of a fatty acid and / or a fatty acid amine salt exhibits an effect of reducing friction even at a blending amount that does not affect the polishing rate.

  The polishing composition of the present invention is allowed to contain any anticorrosive agent. As the anticorrosive, a very small amount of a known substance such as a triazole compound and / or a derivative thereof can be used. However, a feature that makes the present invention stand out further is that a polishing composition that does not require any anticorrosive and no abrasive grains can be provided. That is, even in a composition that does not contain abrasive grains or anticorrosive agents, it is possible to achieve both high polishing performance and excellent anticorrosion performance.

  As the oxidizing agent, peroxide, nitric acid, perchloric acid and the like can be used, and hydrogen peroxide is particularly preferable. This hydrogen peroxide is usually used as a hydrogen peroxide solution added to other polishing composition components immediately before polishing. The hydrogen peroxide content is preferably 10 to 100 parts with respect to 1000 parts of the aqueous medium.

  The aqueous medium used in the chemical mechanical polishing composition of the present invention is typically water and preferably does not contain impurities such as metal ions, and ion-exchanged water or pure water from which impurities are highly removed. Is preferably used.

  Moreover, it is preferable that the polishing composition of the present invention does not contain metals such as sodium, potassium, calcium, magnesium, copper, and iron and metal ions. These metals and metal ions deteriorate the insulating properties of the insulating film, cause a failure such as leakage, and are not preferable for device reliability. The said structure is achieved, for example by using an ultrapure water as an aqueous medium, or selecting the component mix | blended with polishing composition which does not contain the said metal.

  Furthermore, by applying the polishing composition of the present invention to CMP of a copper wiring board, the copper or copper alloy wiring board can be effectively polished, and this CMP step is a process for producing a copper or copper alloy wiring board. Useful for.

Hereinafter, examples in the investigation of the polishing liquid and characteristics of the produced polishing composition will be described.
However, the present invention is not limited to the following examples.
Any improvement or modification of the present invention that can be easily achieved by those skilled in the art is intended to be covered by the present invention.

  First, for the purpose of grasping the polishing performance and characteristics of each substance as a polishing accelerator, 5 parts by weight and 10 parts by weight of each substance are added to 1000 parts of pure water, and this is mixed with a stirrer and then polished. A liquid was obtained.

  In addition, oxalic acid is used as the polishing accelerator of the present invention, and for comparison, substances already known as polishing accelerators (quinaldic acid, citric acid and tartaric acid as oxyacids, glycine and histidine as amino acids) are used. It was.

  To the polishing liquid thus prepared, 100 parts or 10 parts of hydrogen peroxide (31% by weight of hydrogen peroxide water) is added as an oxidizing agent, and polishing of a copper film-formed wafer is performed under the following polishing conditions. Went. In addition, regarding the hydrogen peroxide concentration, a concentration capable of maximizing the polishing performance of each substance already confirmed was used.

[Polishing tester and polishing conditions]
As a polishing apparatus, a CMP experimental machine (plate diameter 610 mm) was used.
The polishing conditions are as follows.
Surface plate speed: 75 rpm
Carrier rotation speed: 78 rpm
Polishing pressure: 7 kPa (1 psi) and 14 kPa (2 psi)
Polishing time: 1 minute Slurry supply amount: 150 ml / min
Polishing pad: IC-1000 / SUBA400 (Rodel Nitta)

  Table 1 shows the polishing liquid composition relating to the polishing rate, and Table 2 shows the evaluation results.

When the polishing accelerator concentration is 0.5%, oxalic acid, oxyacids such as citric acid and tartaric acid show practical polishing rates, especially oxalic acid is extremely superior even under low polishing pressure compared to other substances. The copper polishing rate was shown.
On the other hand, in order to use other substances and exhibit a practical polishing rate, it is necessary to increase the addition concentration or to mix abrasive grains. However, the method is different from the intended direction of the present invention.

  Next, the copper polishing rate was compared when benzotriazole, which is generally used as an anticorrosive, was blended. Table 3 shows the evaluated polishing liquid composition, and Table 4 shows the evaluation results.

When benzotriazole is blended, substances other than oxalic acid, citric acid and tartaric acid have a significantly reduced copper polishing rate and do not exhibit practical polishing performance.
It should be noted that citric acid and tartaric acid showed little decrease in copper polishing rate even when the benzotriazole concentration increased, suggesting that the water-solubilization of copper was maintained in the benzotriazole concentration region examined in this evaluation. .

The polishing mechanism in CMP is manifested by removing a reaction product between a polishing accelerator and copper. That is, it is generally known that the reaction between the polishing accelerator and copper is very important.
In order to promote the reactivity with copper, a substance having more carboxyl groups, specifically, a substance having two or more possesses a tendency to be advantageous. However, when it has other functional groups, it may be influenced by its characteristics, so it does not apply to all.
From the above, in the copper polishing rate evaluation, it was possible to confirm substances that could be used for the polishing abrasive-free polishing liquid.

However, when used in this application, excellent performance is required not only in polishing speed but also in dishing and pad-wafer friction during polishing.
With regard to dishing, focusing on the etching property to copper, which is the main factor, each substance as a polishing accelerator was evaluated using the polarization resistance method and the impedance method of the corrosion electrochemical measurement method.

[Evaluation tester and evaluation conditions]
Evaluation device: 1280B manufactured by Solartron
Electrode: A copper test piece (surface area 1 cm ² ) was used that was insulated with epoxy resin and silicon sealant.
Electrode pretreatment: Tough pitch copper was finally polished at # 1000, degreased by washing with acetone and hexane, immersed in an aqueous nitric acid solution, and washed with pure water.

  Table 5 shows the results (impedance method) in electrochemical corrosion evaluation, and Table 6 shows changes with time in the polarization resistance method of oxalic acid and quinaldic acid.

  A brief description of the electrochemical corrosion evaluation method will be given. Corrosion is a reaction in which electrons are exchanged. When resistance increases, electrons become difficult to exchange. Therefore, it can be said that one way to suppress corrosion is to make it difficult for electricity to flow.

As one of the electrochemical corrosion evaluation methods, the polarization resistance method sweeps a potential of about ± 10 mV around a natural potential shown when copper is immersed in a polishing liquid. This is a method of plotting E (potential) / I (current density) from the current at that time, and the E / I plot is usually a straight line, so that the resistance value is obtained from the slope. The method is performed with a DC voltage.
In this evaluation, a large resistance indicates that electricity does not flow easily, and therefore corrosion is suppressed. However, some resistances are not related to anticorrosion properties, but are also measured by resistance (for example, due to gas generation at the counter electrode (such as platinum)) and solution resistance. In order to determine whether it is present, the frequency response is confirmed by the impedance method, and it is generally confirmed that the film is formed on the surface at less than 10 kHz, and the target resistance is the proportion of the polarization resistance. There is a need to.

  In addition, since this evaluation can be completed in a short time, for example, within 10 seconds, grasp the anticorrosion mechanism in CMP in which the reaction between the polishing accelerator and copper and the removal of the reactant are continuously performed. It can be said that it is useful as one method. However, it is necessary to consider that all the resistances such as the solution resistance described above are also measured.

  Next, the impedance method will be briefly described. This method applies an AC voltage (usually 5-10 mV), sweeps the frequency of the AC voltage from, for example, a high frequency (20 kHz) to a low frequency (0.01 Hz), and plots a vector of real and imaginary components. A Bode diagram showing the diagram, impedance versus frequency and phase of the vector is obtained. Based on the results, an equivalent circuit is estimated, and the capacitance component and resistance of the anticorrosive component are measured. An example of an equivalent circuit is shown in FIG.

  As a result of using the impedance method, oxalic acid and quinaldic acid show high surface resistance. It is suggested that an electrochemical resistance material may be formed on the copper surface. On the other hand, citric acid, tartaric acid, glycine and the like show low resistance values. In addition, with respect to the change with time of the polarization resistance for oxalic acid and quinaldic acid shown in Table 6, the polarization resistance value hardly changes with the passage of time for quinalic acid. It has risen significantly and showed different trends. In this phenomenon, an increase in resistance value indicates an increase in resistance material formed on the copper surface, that is, a reaction product of oxalic acid and copper is formed on the copper surface and increases with time.

5 and 6 show the FT-IR of the wafer surface when the wafer is immersed in a hydrogen peroxide solution of each organic acid and dried. In the case of oxalic acid and quinaldic acid, IR absorption that appears to be a reaction product with Cu was shown on the surface. On the other hand, no reaction product was formed on the surface of citric acid and glycine, and a correlation with the surface resistance value by the impedance method was shown.
As for oxalic acid and quinaldic acid, the results of the formation of a water-insoluble reaction product and the formation of a protective film by itself on the copper surface are obtained from the results of impedance method and FT-IR. In addition, from this result, in the case of the oxyacid which has a hydroxyl group, it is thought that the function which makes the reaction material with copper water-soluble is strong, and etching property becomes high.
From the above, if oxalic acid and quinaldic acid are used, the reaction layer formed on the concave surface of the copper wiring, that is, the protective film increases as polishing progresses, and as a result, copper etching can be suppressed. It was suggested that it has anti-corrosion function.

  Table 7 shows the polarization resistance when benzotriazole is added to oxalic acid alone or to oxalic acid.

  Benzotriazole forms an adsorption / protection film on the copper surface. When used in combination with a polishing accelerator, the reaction between the polishing accelerator and copper is suppressed, and etching is generally reduced. In this evaluation, this protective film is measured as a resistance substance, and benzotriazole alone exhibits a very large resistance value. Therefore, when benzotriazole is included, it generally shows a larger resistance value than the case of the polishing accelerator alone.

  However, in the case of oxalic acid, in particular, the polarization resistance tended to decrease in the range of 0 to 2 minutes, which is important in CMP. This is because oxalic acid has a high ability to form a resistance substance as a protective film by itself. That is, it shows that the reaction between oxalic acid and copper was inhibited by benzotriazole, and the ability of oxalic acid to form a self-protecting film was lowered.

  Further, regarding the composition of Example 4, when the benzotriazole concentration is high, the result that the copper polishing rate is low is obtained even though the polarization resistance is low. This is probably because oxalic acid and copper could not sufficiently react due to the presence of benzotriazole, and the reaction product could not be formed, so that the polarization resistance value was lowered. The polishing rate is expressed by removing the reactant with a pad, that is, the removal amount of the reactant. If the amount of the reaction product itself is small, even if all of the reaction product is removed, the polishing rate will decrease.

From the above considerations, it was clarified that when oxalic acid is used as a polishing accelerator, high anticorrosion ability is exhibited without using benzotriazole.
In order to reduce the friction between the pad and the wafer during polishing, it is useful to add a friction reducing agent, and a fatty acid usually used in a general lubricant is added. Here, caprylic acid was used, and triethanolamine was used in combination in order to increase the solubility in water.

[Polishing tester and polishing conditions]
As a polishing apparatus, a CMP experimental machine (plate diameter 610 mm) was used.
The polishing conditions are as follows.
Surface plate speed: 75 rpm
Carrier rotation speed: 78 rpm
Polishing pressure: 7 kPa (1 psi) and 14 kPa (2 psi)
Polishing time: 1 minute Slurry supply amount: 150 ml / min
Polishing pad: IC-1000 / SUBA400 (Rodel Nitta)

[Method and apparatus for measuring polishing torque]
Torque current was collected from a rotary motor amplifier of the carrier of the polishing apparatus using a PC link type high-performance recorder (GR-3500 manufactured by KEYENCE). The collected data was converted by software (Microsoft EXCEL), and the average torque was calculated. Table 8 shows the studied compositions, and Table 9 shows the polishing torque measurement results.

By blending the friction reducing agent, the polishing torque is reduced, and the blending effect has been confirmed.
On the other hand, even when a friction reducing agent was added, the polarization resistance showed almost the same value, and it was confirmed that the mixing of the friction reducing agent did not affect the reaction between oxalic acid and copper, that is, the anticorrosion performance. The results are shown in Table 10.

  On the other hand, the copper polishing rate tended to decrease. The results are shown in Table 11.

  The polishing mechanism in the present invention is to remove the reaction product of oxalic acid and copper with a pad. This is considered to be because the friction between the pad and the wafer was reduced by the addition of the friction reducing agent, thereby reducing the ability to remove the reactants. However, the copper polishing rate shows a sufficient value.

  In terms of the polishing rate, several substances showing practical values even in the abrasive grain free type could be confirmed by increasing the polishing accelerator concentration. However, the addition of an anticorrosive agent is essential in terms of anticorrosion against copper, and the polishing rate is extremely reduced. If the composition of abrasive grains is assumed, the above performance can be optimized, but the friction during polishing increases.

  From the above results, it became clear that oxalic acid is effective as a substance that can achieve both polishing performance and anticorrosion performance. By using oxalic acid, it became clear that high polishing performance and suppression of dishing can be achieved without necessarily requiring an anticorrosive, and that the conflicting items of polishing friction reduction can be solved.

  (A) is wiring cross-sectional view of Cu wiring board before CMP, (b) is wiring cross-sectional view of Cu wiring board after CMP.   It is a figure which shows dishing.   It is a figure which shows erosion.   It is a figure which shows the general example of an equivalent circuit. In the figure, Rsol is the resistance of the solution, R1 or R2 is a direct current resistance, and C1 and C2 are capacitance components.   It is a FT-IR chart of 3 samples. Top: A diagram showing cupric oxalate (reagent). Middle: The wafer surface is shown after the wafer has been dipped in a solution of 0.5% oxalic acid, 0.2% benzotriazole, and 10% hydrogen peroxide for 3 minutes and dried. Bottom: It is a view showing the wafer surface after the wafer was immersed in a solution of 0.5% oxalic acid and 10% hydrogen peroxide for 3 minutes and dried.   It is a figure which shows the result of having analyzed the surface of the wafer by FT-IR after immersing and drying the wafer for 3 minutes in the liquid which added the hydrogen peroxide to the oxalic acid, the quinaldic acid, the glycine, and the citric acid.

Explanation of symbols

1 Insulating film 2 Barrier metal film 3 Cu wiring part

Claims (9)

  A polishing composition comprising a polishing accelerator, an aqueous medium, and an oxidizing agent having a polishing accelerating property and an anticorrosive function for metals, and containing no abrasive grains.   The polishing composition according to claim 1, further comprising no anticorrosive.   The polishing composition according to claim 2, wherein the anticorrosive is a triazole compound and / or a derivative thereof.   The polishing composition according to claim 1, wherein the polishing accelerator comprises a carboxylic acid and / or a salt thereof.   The polishing composition according to claim 4, wherein the carboxylic acid and / or salt thereof is oxalic acid.   Furthermore, the polishing composition of Claims 1-5 containing a friction reducing agent.   The polishing composition according to claim 6, wherein the polishing friction reducing agent is a fatty acid and / or an amine salt of a fatty acid.   A metal polishing method using the polishing composition according to claim 1.   The polishing method according to claim 8, wherein the metal is mainly composed of copper or a copper alloy.

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