CN101481640B - Aqueous cleaning composition - Google Patents

Abstract

An aqueous cleaning composition for use in a chemical mechanical planarization process or a subsequent cleaning process in an integrated circuit copper process, comprising 0.1 wt% -20 wt% of an aminomethane, 0.05 wt% -20 wt% of a quaternary ammonium compound and water; when used in a semiconductor planarization process or a subsequent cleaning process, the aqueous cleaning composition of the present invention can effectively remove contaminants and reduce the number of defects on the surface of a wafer, and can maintain a better surface roughness of the wafer.

Description

aqueous cleaning composition

technical field

The invention relates to an aqueous cleaning composition, in particular to an aqueous cleaning composition used for chemical mechanical planarization (CMP) treatment in integrated circuit manufacturing processes.

Background technique

With regard to semiconductor elements, they are currently developing toward smaller line widths and higher integration densities. When the minimum line width of an integrated circuit is reduced to below 0.25 microns, the time delay (RCdelay) caused by the resistance of the metal wire itself and the parasitic capacitance of the dielectric layer has become the main key affecting the operation speed of the component. Therefore, in order to improve the computing speed of components, the industry has gradually replaced the traditional aluminum-copper alloy wires with copper metal wires in the high-end process below 0.13 microns, and this process is called "copper process" for short.

Applying chemical mechanical planarization (CMP) technology to copper metal wire manufacturing process can not only overcome the problem of difficult pattern definition due to copper metal etching is difficult, but also form a global planarity plane after grinding, Conducive to the implementation of multi-layer wiring process. The principle of chemical mechanical planarization is to use the abrasive particles in the polishing liquid to cooperate with chemical additives to cause abrasion on the surface material of the wafer, so that the higher part of the uneven surface will have a high removal rate due to high pressure , the lower part of the uneven surface has a slower removal rate due to less pressure, and achieves the purpose of global planarization.

During the polishing process of chemical mechanical planarization, a large number of fine abrasive particles and chemical additives in the polishing liquid, as well as debris peeled off by wafer abrasion, may adhere to the wafer surface. Generally, the common pollutants after wafer grinding are metal ions, organic compounds or abrasive particles. If there is no effective cleaning procedure to remove the above pollutants, it will affect the progress of the subsequent process and reduce the yield and reliability of the device. Therefore, the cleaning process during or after the CMP process has become a key technology for the successful application of CMP to the semiconductor process.

Benzotriazole (BTA for short) or its derivatives are often used as corrosion inhibitors in the polishing liquid for copper manufacturing process. Among the pollutants produced after copper process wafer grinding, BTA organic residues are the most difficult to remove, mainly because BTA is bonded to copper wires by chemical adsorption. Traditional physical removal methods such as electrostatic repulsion, ultrasonic vibration, and polyvinyl alcohol (PVA) brush scrubbing are not easy to have a good cleaning effect.

Conventional inter-metal dielectric layers and tungsten plugs (W plugs) are often cleaned with ammonia solution, citric acid solution and/or fluorine-containing compounds after chemical mechanical planarization, but these solutions do not Suitable for wafers with copper metal leads. Ammonia solution will corrode the surface of copper metal unevenly, resulting in roughening. The solubility of citric acid aqueous solution to copper is too poor and there is still room for improvement in the removal rate of pollutants. Fluorine-containing compounds such as hydrofluoric acid will not only roughen the copper surface, but in order to avoid harming the human body and the environment, more costs must be paid for personnel safety protection and waste liquid treatment.

U.S. Patent No. 6,498,131 to Small et al. discloses a composition for removing CMP residues comprising an aqueous solution having a pH of 10 to 12.5, the aqueous solution comprising at least one nonionic surfactant, at least one Amine, at least one quaternary ammonium compound, and at least one surface retention agent selected from the group consisting of ethylene glycol, propylene glycol, polyethylene oxide, polypropylene oxide and mixtures thereof, the amine can be, for example, monoethanolamine (monoethanolamine, referred to as MEA) wait.

U.S. Patent No. 6,492,308 of Naghshineh et al. discloses a cleaning solution for cleaning copper-containing integrated circuits, which is composed of a C ₁ -C ₁₀ tetraalkylammonium hydroxide (quaternary ammonium hydroxide), a polar organic amine and a corrosion inhibitor, the polar organic amine can be selected from monoethanolamine and the like.

U.S. Patent No. 5,988,186 to Ward et al. discloses an aqueous cleaning composition for removing organic or inorganic substances, comprising a mixture of water, a water-soluble polar solvent, an organic amine, and a Alcohol ester corrosion inhibitor with benzene ring structure, the organic amine disclosed in the description includes tetraalkylammonium hydroxide, diamine or monoamine hydroxyl compound, etc.

U.S. Patent Publication No. 2007/0066508 (Chinese Taiwan Patent Publication No. 200641121) by Chen et al. discloses an aqueous cleaning composition for cleaning copper-containing wire wafers after chemical mechanical planarization in integrated circuit manufacturing processes, which consists of It is composed of a nitrogen-containing heterocyclic organic base, an alcohol amine and water.

U.S. Patent Publication No. 2006/0229221 (Chinese Taiwan Patent Publication No. 200706647) of Walker et al. discloses a cleaning composition for cleaning microelectronic substrates, which is composed of quaternary ammonium hydroxide, an alkanolamine ( alkanolamine) and water, the quaternary ammonium hydroxide is preferably selected from tetramethylammonium hydroxide (TMAH), tetrabutylammonium hydroxide or a mixture thereof, and the alkanolamine Preferably, it is selected from monoethanolamine, 1-amino-2-propanol, 2-(methylamino)ethanol, triethanolamine or a mixture thereof.

With the progress of semiconductor wafer manufacturing process, the width of metal wires has been reduced to 32 nanometers. There are still many problems to be overcome in the new planarization process. For example, the surface roughness of the wafer surface with nanometer wire width may become worse after processing. And the results of the electrical test (open/short test) and reliability test (reliability test) of the copper wire wafer become worse after the line width is reduced. The industry still needs a cleaning composition for the copper wire wafer cleaning process that is more effective than the prior art in removing residual pollutants on the copper wire wafer surface and reducing the number of defects on the wafer surface.

Contents of the invention

The applicant considers that although ammonia or amine groups have strong etching properties for copper, how to properly control the etching properties of amines for copper is a difficult problem. Erosion of copper uniformly should solve the above problems. Although some of the aforementioned patents have used alcohol amines (such as monoethanolamine (MEA)) with both amine and hydroxyl groups as cleaning components, the applicant found after actual testing that using such alcohol amines to clean copper wire wafers When there are pollutants on the surface, there will be problems of strong corrosion of copper wafers and obviously high surface roughness.

The applicant found surprisingly in the process of solving the above problems that when using another class of aminomethane (i.e. dimethylolaminomethane (2-amino-1, 3-propane diol) and / or trishydroxymethylaminomethane (2-amino-2-(hydroxymethyl)-1,3-propanediol) in combination with traditional cleaning quaternary ammonium compounds, as long as the content relationship between the two is regulated at a specific In the range, it can achieve excellent pollutant removal rate, and will not damage the surface roughness, and the ability to dissolve copper is also better than previous cleaning agents.

The object of the present invention is to provide an aqueous cleaning composition, which is especially suitable for chemical mechanical planarization in copper processing or its subsequent cleaning procedures, the composition comprising 0.1wt%-20wt% of monoaminomethane, 0.05wt%- 20 wt% of a quaternary ammonium compound, and water; the aminomethane is selected from dimethylolaminomethane, trishydroxymethylaminomethane or a combination thereof.

Aqueous cleaning composition according to the object of the invention, characterized in that the aminomethane is trismethylolaminomethane.

Aqueous cleaning composition according to the object of the present invention, characterized in that the quaternary ammonium compound is a tetraalkylammonium hydroxide.

The aqueous cleaning composition according to the object of the present invention is characterized in that the quaternary ammonium compound is selected from tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide or combinations thereof.

Aqueous cleaning composition according to the object of the present invention, characterized in that the quaternary ammonium compound is tetramethylammonium hydroxide.

The aqueous cleaning composition according to the object of the present invention is characterized in that the aminomethane content is 0.1wt%-15wt%.

The aqueous cleaning composition according to the object of the present invention is characterized in that the aminomethane content is 0.1wt%-10wt%.

The aqueous cleaning composition according to the object of the present invention is characterized in that the content of the quaternary ammonium compound is 0.05wt%-15wt%.

The aqueous cleaning composition according to the object of the present invention is characterized in that the content of the quaternary ammonium compound is 0.05wt%-10wt%.

The aqueous cleaning composition according to the object of the present invention is characterized in that it further comprises a nitrogen-containing heterocyclic organic base.

Aqueous cleaning composition according to the object of the present invention, characterized in that the nitrogen-containing heterocyclic organic base is piperazine.

The beneficial effect of the present invention is that: the water-based cleaning composition of the present invention is contacted with the copper-containing semiconductor wafer after chemical mechanical planarization and grinding for an effective period of time to effectively remove the pollutants remaining on the surface of the wafer after grinding, At the same time, the better surface roughness of the copper wire is maintained. Another beneficial effect of the present invention is: no need to use surfactants and corrosion inhibitors (such as BTA and/or its derivatives and ascorbic acid, etc.) used to protect the copper metal surface in the cleaning process, can effectively It can effectively remove the pollutants remaining on the wafer surface after grinding, and can avoid the problem of surfactants and corrosion inhibitors remaining on the wafer.

Detailed ways

Preferably, the aminomethane is trismethylolaminomethane.

Preferably, the quaternary ammonium compound is tetraalkylammonium hydroxide, more preferably tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide or a combination thereof. In an embodiment of the present invention, the quaternary ammonium compound is tetramethylammonium hydroxide.

Optionally, the aqueous cleaning composition may further comprise a nitrogen-containing heterocyclic organic base. Preferably, the nitrogen-containing heterocyclic organic base is piperazine.

Regarding the concentration of aminomethane and quaternary ammonium compounds in the aqueous cleaning composition of the present invention, generally in order to save production, transportation and storage costs, manufacturers usually provide a higher concentration of the composition, and then dilute it with ultrapure water at the end of use Use after about 1-60 times. In the case of special needs, such as saving processing time, the stock solution of the cleaning composition with a higher concentration can be directly used to clean the wafer.

The cleaning composition of the present invention can be used at normal temperature, and the cleaning composition is in contact with the copper-containing semiconductor wafer for an effective period of time, which can effectively remove the pollutants remaining on the surface of the wafer while maintaining a better surface of the copper wire roughness. Generally speaking, when the concentration is low, a longer contact time (for example, 1-3 minutes) is required, and when the concentration is high, only a short contact time (for example, less than 1 minute) is required. In actual use, users can seek process optimization of cleaning composition concentration and contact time according to needs.

Taking all factors of manufacture, transportation and use into consideration, the content of aminomethane in the composition is 0.1wt%-20wt%, more preferably 0.1wt%-15wt%, based on the total weight of the composition, Still more preferably 0.1wt%-10wt%.

Also in consideration of the above factors, based on the total weight of the composition, the content of the quaternary ammonium compound in the composition is 0.05wt%-20wt%, more preferably 0.05wt%-15wt%, and more preferably 0.05wt% %-10wt%.

What is exemplified in each specific example of the present invention is a concentration that is relatively dilute but has reached the purpose. Those skilled in the art will understand that when using a cleaning composition with a higher absolute concentration, it can still reach the purpose of the present invention. , and the timeliness will be better, but the cost of raw materials is higher.

As mentioned earlier, the corrosion inhibitors (such as BTA or its derivatives) used in the polishing liquid for chemical mechanical planarization of copper process will remain on the wafer surface after polishing, and the organic residues are difficult to remove It is generally removed by physical methods such as electrostatic repulsion, ultrasonic vibration and polyvinyl alcohol (PVA) brush scrubbing. The aminomethane and quaternary ammonium compounds contained in the cleaning composition of the present invention can increase the saturation solubility of the cleaning composition for organic residues (such as BTA), thereby providing a greater driving force to dissolve BTA particles. Therefore, the above traditional physical removal method can achieve better cleaning results when used in conjunction with the cleaning composition disclosed in the present invention.

The cleaning composition of the present invention can be used to clean the flattened wafer surface on a chemical mechanical planarization machine, or can be used to clean the flattened wafer surface on an independent cleaning machine.

Example

The present invention will be further described with reference to the following examples, but it should be understood that the examples are for illustration only and should not be construed as limitations on the practice of the present invention.

efficacy test

The same test carried out for each aqueous cleaning composition prepared by each of the following examples and comparative examples is as follows:

I. Test of copper dissolving ability

A copper blank wafer is cut into a wafer of 1.5 cm in length and width, and the wafer is pre-treated with acid dissolution to remove the copper oxide on the surface layer, and then the wafer is soaked in 50 ml of aqueous cleaning composition, and taken out after one minute wafer, and the concentration of copper ions in the solution was measured by ICP-MS.

II. BTA Saturation Solubility Test

Put the aqueous cleaning composition in an environment with a constant temperature of 25°C, add excess BTA to stir and dissolve, filter out the insoluble matter in the cleaning composition after 4 hours, and analyze the BTA in the solution by high performance liquid chromatography (HPLC) concentration.

III. Measurement of Surface Roughness

The aqueous cleaning composition was used to clean the ground copper blank wafer on the cleaning machine Ontrak. The cleaning time was 2 minutes, and the flow rate of the cleaning composition was 600 ml per minute. After cleaning, the surface roughness (average roughness Ra and root mean square roughness Rq) of the copper wafer was measured with an atomic force microscope (AFM).

IV. Removal Efficiency Test of Surface Particulate Contaminants

Copper blank wafers were contaminated by immersion in a copper process slurry containing the corrosion inhibitor BTA for 1 minute. After contamination, rinse with ultrapure water on Ontrak cleaning machine for 18 seconds, then spin dry, and then measure the particle number A on the contaminated wafer with TOPCON WM-1700 wafer particle measuring instrument. The wafer with known number of particles after contamination was scrubbed on the cleaning machine Ontrak with different cleaning compositions for 2 minutes, and finally rinsed with ultrapure water for 18 seconds, then spin-dried, and measured again with TOPCONWM-1700 wafer particle measuring instrument The particle number B on the wafer after cleaning, and then calculate the removal rate of each cleaning composition on the particle contamination on the wafer surface (removal rate=((A-B)/A)×100%).

<Example 1-5 and Comparative Example 1-3>

According to the components of each embodiment in Table 1 and the dosage ratio (all in wt %), the cleaning composition of the original composition is first prepared, and then diluted 30 times into the cleaning composition for testing, and the previous technology in Table 1 The used cleaning composition containing diethanolamine, triethanolamine and piperazine (comparative example 1); commonly used citric acid cleaning agent (comparative example 2); The copper dissolving ability, BTA saturation solubility, wafer surface roughness after cleaning, and the removal rate of surface particulate pollutants of the cleaning compositions of each embodiment and comparative example were evaluated. These results are listed in Table 1.

Results and Discussion

As can be seen from the results of Table 1, trismethylolaminomethane has the ability of etching and dissolving copper metal, which can increase the etching dissolution rate of copper metal; as can be seen from the results of Example 5, the addition of (nitrogen-containing heterocyclic organic base) can Improve the saturation solubility of BTA in cleaning compositions. From the results of Comparative Examples 2 and 3, it can be seen that citric acid and water have no ability to dissolve copper metal. The stronger the copper metal dissolving ability and the higher BTA saturation solubility of the cleaning composition, the better the cleaning effect on the pollutants on the copper metal and the organic pollutants such as BTA, but the improper copper metal etching dissolving ability (too much Fast and/or non-uniform) have a negative impact on roughness.

Comparing the cleaning compositions of Examples 1 to 5 with Comparative Examples 1 to 3, it can be seen that although a larger amount of amines will increase the surface roughness, it still remains close to or better than the prior art (Comparative Examples 1, 2). Surface roughness level. It shows that the cleaning composition of the present invention can not only etch and dissolve copper metal in a wide concentration range, but also maintain good surface roughness of copper metal. Furthermore, although citric acid (comparative example 2) or the alcohol amine of the prior art plus nitrogen-containing heterocyclic organic base composition (comparative example 1) can be used alone, most of the pollutants can be removed, but when trimethylolamine When methane and tetramethylammonium hydroxide are used together (Examples 1-4), the cleaning effect can be greatly improved.

In summary, the specific type of aminomethane used in the composition of the present invention has not only an amine group but also a hydroxyl group, and the presence of the hydroxyl group can reduce the etching ability of the amine group for copper, so it can also protect the copper surface at the same time. The mechanism of etching and protection is formed at the same time, so the copper surface can be uniformly corroded without degrading the roughness of the copper surface after being combined with quaternary ammonium compounds, and the pollutant removal rate exhibited is much superior to that of previous cleaning compositions.

Table 1

Original composition (wt%) Composition after 30-fold dilution (wt%)   Acid-base value (pH) after 30-fold dilution Copper Solubility (ppb) BTA saturated solubility (%) Surface roughness Ra(nm) Surface roughness Rq(nm) Pollutant removal rate trishydroxymethylaminomethane tetramethylammonium hydroxide other components trishydroxymethylaminomethane tetramethylammonium hydroxide other components Example 1 5.0% 2.5% - 0.16% 0.08% - 11.88 24.80 2.17 0.784 1.032 93.24% Example 2 5.0% 10.0% - 0.16% 0.33% - 12.40 27.17 2.60 0.829 1.064 96.32% Example 3 10.0% 2.5% - 0.33% 0.08% - 11.89 37.67 2.29 0.803 1.123 93.63% Example 4 10.0% 10.0% - 0.33% 0.33% - 12.41 29.90 2.83 0.862 1.121 95.46% Example 5 10.0% 10.0% Piperazine 7.0% 0.33% 0.33% Piperazine 0.23% 12.44 30.60 3.33 0.734 0.999 94.49% Original composition (wt%) Composition after 30-fold dilution (wt%) Comparative example 1 Diethanolamine 10.0% Triethanolamine 10.0% - Piperazine 9.0% Diethanolamine 0.33% Triethanolamine 0.33% - Piperazine 0.3% 11.01 23.07 3.25 0.987 1.150 82.39% Comparative example 2 Aqueous solution of citric acid 30.0% Citric acid aqueous solution 1.0% 3.89 <2 - 0.872 1.087 88.18% Comparative example 3 Ultra-pure water Ultra-pure water 7.73 <2 - 0.718 1.101 0%

Claims (11)

1. an aqueous clean combination is characterized in that, comprises the amido methane of 0.1wt%-20wt%, a quaternary ammonium compound and the water of 0.05wt%-20wt%; This amido methane is to be selected from dihydroxymethyl amido methane, tri methylol amino methane or its combination.

2. aqueous clean combination according to claim 1 is characterized in that, this amido methane is tri methylol amino methane.

3. aqueous clean combination according to claim 1 is characterized in that this quaternary ammonium compound is a tetraalkylammonium hydroxide.

4. aqueous clean combination according to claim 3 is characterized in that, this quaternary ammonium compound is selected from tetramethyl ammonium hydroxide, tetraethyl ammonium hydroxide, tetrapropylammonium hydroxide or its combination.

5. aqueous clean combination according to claim 4 is characterized in that this quaternary ammonium compound is a tetramethyl ammonium hydroxide.

6. aqueous clean combination according to claim 1 is characterized in that, the content of this amido methane is 0.1wt%-15wt%.

7. aqueous clean combination according to claim 6 is characterized in that, the content of this amido methane is 0.1wt%-10wt%.

8. aqueous clean combination according to claim 1 is characterized in that, the content of this quaternary ammonium compound is 0.05wt%-15wt%.

9. aqueous clean combination according to claim 8 is characterized in that, the content of this quaternary ammonium compound is 0.05wt%-10wt%.

10. aqueous clean combination according to claim 1 is characterized in that, also comprises a nitrogen heterocyclic ring organic bases.

11. aqueous clean combination according to claim 10 is characterized in that, this nitrogen heterocyclic ring organic bases is a piperazine.