KR20060102244A - Composition for cleaning semiconductor device - Google Patents

Abstract

The present invention relates to a composition for cleaning semiconductor devices, including semiconductor devices, silicon wafers, LCDs, photomasks, and the like, and more specifically, to semiconductor substrates (Devices, Si wafers, LCDs, The present invention relates to a cleaning composition for a semiconductor device containing an oxidizing agent, an ultrapure water, and a surfactant in citric acid, which is an organic acid, for cleaning metal impurities, including photo masks, and preventing corrosion of metal wires.

 Semiconductor device, particle adsorption, metal impurity contamination, cleaner

Description

Composition for cleaning semiconductor device

FIG. 1 is a graph illustrating particle resorption prevention effect according to the addition of a surfactant in Example 1. FIG.

Figure 2 is a graph measuring the particle cleaning effect according to the concentration of hydrofluoric acid in Example 2.

3 is a graph measuring the oxidizing power of hydrogen peroxide and ozone in citric acid in Example 3.

Figure 4 is a graph measuring the solubility of ozone in ultrapure water and citric acid in Example 3.

Figure 5 is a graph measuring the delay rate of decomposition of ozone by citric acid in Example 3.

FIG. 6 is a graph measuring the degradability of citric acid by ozone in Example 3. FIG.

FIG. 7 is a graph illustrating a metal oxide cleaning effect of an ozone-containing cleaning composition in Example 3. FIG.

8 is a graph measuring the cleaning effect of the metal oxide of the cleaning composition in Example 4.

9 is a graph measuring the effect of preventing particle resorption of the cleaning composition of Example 4.

 The present invention relates to a composition for cleaning semiconductor devices including semiconductor devices, silicon wafers, LCDs, photomasks, and the like, and more specifically, to semiconductor substrates (Devices, Si wafers, LCDs, The present invention relates to a cleaning composition for semiconductor devices containing oxidizing agent, ultrapure water, and surfactant in citric acid, which is an organic acid, for the cleaning of metal impurities (including photomask) and the corrosion prevention of metal wiring.

In the semiconductor industry, metal ion contamination, particle contamination, and organic material contamination have emerged as major factors in yield reduction, as feature sizes of device polysilicon gates decrease. It is becoming. In addition, as the pattern size of devices increases from megabits (Gbit) to gbit dynamic random access memory (DRAM), the importance of pollution management and management costs are exponentially increasing. . Therefore, the RCA cleaning method is most widely used as a cleaning method for suppressing deterioration of product quality and yield reduction due to contamination factors due to miniaturization of circuit patterns. The RCA cleaning method is divided into SC1 process using aqueous ammonia and hydrogen peroxide solution for removing particles and low molecular weight organic matter and SC2 process using aqueous hydrochloric acid and hydrogen peroxide solution for metal impurity removal. Megasonics with frequencies in the MHz range may be used together to enhance the cleaning effect. However, SC2 cleaning, which is usually used in the post-processing of SC1, is highly corrosive to wiring metals (copper, tungsten, etc.) because hydrochloric acid, which is a strong acid, is used together with hydrogen peroxide. Since the shape cannot be obtained and the pH is 1 or less, adsorption of silica, alumina, and other organic particles onto the silicon surface can be easily generated from the point of view of zeta potential. It is a problem to adversely affect the quality and quality. In addition, while the required level of metal impurity removal is rising, the SC2 cleaning method is performed through substitution reaction with an element existing while forming a lattice with one silicon in the silicon oxide layer, such as aluminum, or with silicon atoms such as copper, gold, and platinum. For metal ions that are directly bonded and require large oxidation energy in order to break and ionize them, the required level cannot be satisfied. Problems in use include harmful gases generated from hydrochloric acid, causing health problems for workers and corrosion of expensive cleaning equipment, and corrosion of these cleaning equipment may cause secondary contamination. To prevent this, it is inevitable to increase the displacement in the clean room.

The purpose of the present invention is to introduce citric acid, an organic acid, and to resorption of particles and aluminum and precious metals, basically to solve the environmental problems of the existing SC2 cleaning solution (also called "HPM") and corrosion of metal wiring. In order to solve the problem of lack of cleaning power for a semiconductor device cleaning composition containing a fluorine-based surfactant, ozone, hydrofluoric acid solution.

In order to achieve the above object, the present inventors presently use a SC2 cleaning solution (hydrochloric acid / hydrogen peroxide) for cleaning metal impurities of semiconductor substrates (including semiconductor silicon substrates (Si wafer), liquid crystal glass substrates, and quartz substrates for photomasks). / Mixture of ultrapure water) causes problems of adsorption of particles during cleaning and corrosion of expensive cleaning equipment by the generation of hydrochloric acid vapors, and solves the problems of cost and cost due to the treatment of waste solution of hydrochloric acid and hydrogen peroxide. To further strengthen, a semiconductor cleaning composition containing citric acid was developed.

The present invention is i) 3 to 5% by volume 10% citric acid as organic acid; Ii) 3-7% by volume of 31% hydrogen peroxide or 1-150 ppm ozone as oxidizing agent; Iii) one or two or more additives selected from the group consisting of fluorine-based anionic surfactants, hydrofluoric acid and ammonium fluoride to prevent adsorption of particles; And iii) residual ultrapure water; It relates to a semiconductor device cleaning composition containing.

In addition, the present invention is characterized in that the fluorine-based anionic surfactant is a fluoroalkylsulfonamide compound.

In addition, the present invention is characterized in that the additive is a fluorine-based anionic surfactant 10 ~ 1000ppm, 49% hydrofluoric acid 10ppm ~ 250ppm, ammonium fluoride is 10 ~ 500ppm.

As the fluorine-based surfactant, any anionic surfactant that does not have a metal ion as a salt can be used, and carboxylate, sulfonate, sulfate ester salt, and phosphate ester salt are preferable. In particular, the fluoroalkylsulfonamide compounds of the formulas (1) and (2) are more preferred. The surfactants represented by the following Chemical Formulas 1 and 2 do not contain metals such as sodium, potassium, and calcium.

R ^l SO ₂ NR ² -XH

R ^l SO ₃ ^- NR ₄ ⁺

Wherein R ¹ is a fluoroalkyl group, R ² is a hydrogen atom or a lower alkyl group, X is CH ₂ COO or (CH ₂ CH ₂ O) _n , and n is an integer of 1 to 20. And R ₄ is an alkyl group having ₁ to ₄ carbon atoms.

Hereinafter, the configuration of the present invention will be described in detail by examples. However, the scope of the present invention is not limited to the above embodiment.

Use solution

In the following examples, 10% citric acid solution, 31% hydrogen peroxide, 37% hydrochloric acid, 49% hydrofluoric acid was used.

Example 1 Citric Acid / Hydrogen Peroxide / Ultra Pure Water / Surfactant Composition

In this example, 100 ppm of ammonium perfluoroalkylsulfonate was added to a 70 L solution of citric acid (10% stock solution) / hydrogen peroxide (31% stock solution) / ultra pure water at a volume ratio of 3/4/63. A composition for preparation was prepared. As a control, 70 L of HPM solution prepared by mixing hydrochloric acid (using 37% stock solution) / hydrogen peroxide (using 31% stock solution) / ultra pure water at a volume ratio of 3/4/63 was prepared.

To the 70-L container made of quartz filled with the composition, add 0.08 to 0.11 µm of particles (particles mixed with silica / alumina = 1/1) so that the number of particles per 1 ml volume is 30000, and 8 inches for 10 minutes. After depositing the wafer and rinsed with ultrapure water for 6 minutes in a separate 70 L quartz container and spin-dried, only particles of 0.11 μm or more were measured using Tencor 6220 and the results are shown in the graph of FIG. 1.

Example 2: Citric Acid / Hydrogen Peroxide / Ultrapure Water / Hydrofluoric Acid Composition

2-1. Determination of Metal Impurities Cleaning Efficiency According to HF Addition Concentration

Five 70L mixtures of citric acid / hydrogen peroxide / ultra pure water (3/4/63, volume ratio) were prepared, respectively, and a cleaning composition was added with 0 ppm, 60 ppm, 120 ppm, 250 ppm, 300 ppm, and 350 ppm of HF (49% stock solution), respectively. It was prepared and used to measure the cleaning efficiency for the metallic impurities.

In the cleaning method, an 8-inch silicon wafer (initial wafer) artificially contaminated to maintain a certain level on the surface of the silicon wafer was deposited for 6 minutes in a 70-liter container made of quartz using citric acid cleaning composition containing different concentrations of HF. After washing, the resultant was rinsed with ultrapure water for 6 minutes in a separate 70 L quartz container, followed by spin drying.

In order to analyze this, the metal ions on the wafer surface were extracted using a mixture of hydrofluoric acid and hydrogen peroxide and analyzed by ICP-MS. The results are shown in Table 1 below.

2-2. Measurement of Particle Cleaning Effect According to HF Addition Concentration

Five 70L mixtures of citric acid / hydrogen peroxide / ultra pure water (3/4/63, volume ratio) were prepared, respectively, and a cleaning composition was added with 0 ppm, 60 ppm, 120 ppm, 250 ppm, 300 ppm, and 350 ppm of HF (49% stock solution), respectively. It was prepared and the particle cleaning effect was measured using it.

For the particle induction test, the 8-inch wafer was immersed for 10 minutes in the cleaning composition to which each concentration of HF was added, followed by rinsing with ultrapure water for 6 minutes in a separate 70 L quartz container and spin-drying.

The dried wafer was measured with particles having a size of 0.065 μm or more using SP1 and shown in FIG. 2.

Through the results of the present embodiment, the cleaning composition has improved metal impurity cleaning power by the interaction of citric acid and hydrofluoric acid (HF), and the hydrofluoric acid and ammonium fluoride (including NH ₄ F and NH ₄ F.HF) are silicon or silicon oxide film. The ability to etch compensates for the lack of citric acid's detergency for aluminum and copper contaminants present in the oxide film. In addition, the problem of causing particle generation, which is a problem of using the existing hydrofluoric acid was able to manage the particle contamination by adding a concentration of hydrofluoric acid below 250ppm. Therefore, when the hydrofluoric acid was added at 250 ppm or less, and NH ₄ F and NH ₄ F.HF were added at 500 pm or less in the final cleaning solution, particle generation was suppressed and the cleaning effect on the metallic impurities could be maximized.

Example 3: Cleaning Composition Containing Ozone as Oxidizer

In this embodiment, ozone was used as an oxidizing agent to prepare a cleaning composition and its properties were investigated. The cleaning composition of the present invention is an environmentally friendly formulation that significantly improves the cleaning power of metal ions compared to HPM by removing ozone peroxide and using ozone as an oxidizing agent.

3-1. Comparison of Oxidation Capacity between Hydrogen Peroxide Containing Citric Acid and Ozone Water

Citric acid / ultra pure water = 3/67 (volume ratio, citric acid: 10% stock solution) and 16 ppm of ozone were dissolved. As a control, a solution of citric acid / hydrogen peroxide / ultra pure water = 3/4/63 vol. 3 is shown. As can be seen in FIG. 3, the oxidation degree of the solution using ozone as the oxidant was found to be much higher than that of hydrogen peroxide.

3-2. Ozone solubility measurement by citric acid

A washing liquid having a volume ratio of citric acid / ultra pure water = 3/67 was prepared and dissolved ozone in a bubbling manner. As a control, ozone was dissolved in 20 L ultrapure water for 1 hour by bubbling.

Each of the two solutions was shown in FIG. 4 by measuring the solubility of ozone using a UV-vis spectrometer. In Figure 4 it was confirmed that the solubility of ozone in citric acid is much higher.

3-3. Delayed Effect of Ozone Decomposition by Citric Acid

For the ozone solubility experiment with citric acid, two groups of ultrapure water containing 20 ppm of ozone and two groups of citric acid aqueous solution containing citric acid (citric acid / ultra pure water = 3/67 volume ratio) were prepared and each of 1 group of ultrapure water and citric acid solution was used. The group measured the concentration of ozone over time while leaving the container without static pressure (static state), and the remaining group 1 measured the concentration of ozone over time while stirring with a stirrer. The measurement was carried out using UV-vis and the results are shown in FIG. 5.

In FIG. 5, it was confirmed that the solubility of ozone dissolved in citric acid solution was high in both the group using the stirrer and the group left.

3-4. Confirm the possibility of decomposition of citric acid by ozone

In the citric acid aqueous solution containing 6% hydrogen peroxide and 100ppm ozone, the concentration of citric acid was measured at each time period using IC (Ion Chromatography), and the results are shown in FIG. 6. As a result, it was confirmed that no decomposition of ozone occurred.

3-5. Metal impurity cleaning power measurement

1) Composition of HPM: hydrochloric acid / hydrogen peroxide / ultra pure water = 3/4/63 volume ratio (using hydrochloric acid: 37%, hydrogen peroxide: 31% concentration)

2) citric acid / ultra pure water = 3/67 volume ratio (citric acid: 10% stock solution), ozone concentration = 20ppm

3) citric acid / hydrogen peroxide / ultra pure water = 3/4/63 by volume

4) Cleaning method: 8-inch silicon wafer (initial wafer), which artificially contaminated metal impurities to maintain a certain level on the surface of silicon wafer, was immersed and cleaned for 6 minutes in a 70-liter container made of quartz using each cleaner. Rinse with ultrapure water for 6 minutes in a 70 liter quartz vessel and spin-dry.

The wafer was extracted with metal ions on the surface of the wafer using a mixture of hydrofluoric acid and hydrogen peroxide, and analyzed by ICP-MS and shown in FIG. 7.

 The advantage of improving the cleaning ability of metal impurities using ozone as citric acid is that it can improve the saturation concentration up to 5 times from 25ppm to 110ppm only by simple bubbling of ozone, and it can make the most use of ozone oxidizing power. This is due to the fact that it can delay the decomposition rate. At the same time, citric acid itself was not decomposed by the high oxidizing power of ozone.

Example 4: citric acid / ozone / ultra pure water / surfactant / fluoric acid

All effects of citric acid, ozone, hydrofluoric acid and surfactant applications can be expected.

4-1. Metal Impurity Cleaning Experiment

A cleaning composition was prepared by adding 20 ppm of ozone, 200 ppm of fluoric acid, and 100 ppm of ammonium perfluoroalkylsulfonate as a surfactant to 70 L of a mixed solution of citric acid / ultra pure water in a volume ratio of 3 // 67. As a control, HPM was mixed with hydrochloric acid / hydrogen peroxide / ultra pure water at a volume ratio of 3/4/63 (hydrochloric acid: 37%, hydrogen peroxide: 31% stock solution, HRM solution).

The 8-inch silicon wafer (initial wafer), which was artificially contaminated to maintain the surface of the silicon wafer, was immersed in a 70-liter container made of quartz for 6 minutes using the respective cleaners, and then placed in ultra-pure water in a separate 70-liter container. Rinse for minutes and spin dry.

The dried wafer was extracted with metal ions on the surface of the wafer using a hydrofluoric acid and hydrogen peroxide mixture and analyzed by ICP-MS, and is shown in FIG. 8.

4-2. Particle resorption prevention effect measurement

The particle resorption prevention effect was measured using the cleaning composition of 4-1.

Into a 70-liter container of quartz filled with each detergent, add particles (silica / alumina = 1/1 mixed particles) with a size of 0.08 to 0.11 μm so that the number of particles per ml is 30000. After immersion, the resultant was rinsed with ultrapure water for 6 minutes in a separate 70 L quartz container, followed by spin drying.

The dried wafer was measured only with particles of 0.11 μm or larger using Tencor 6220, and the results are shown in FIG. 9. As a result, it was confirmed that the particle residual ratio is significantly lower than the control HRM solution.

Compared to SC2 based on hydrochloric acid (hereinafter referred to as “HPM”, pH of about 0.2 to 0.5), the semiconductor cleaning composition of the present invention has a relatively high pH of about 2.3 in terms of zeta potential. The cleaning effect on the metal ions has a similar advantage, and the erosion rate for the metal wiring made of aluminum and tungsten is 3 kW / min or less, which is significantly lower than that of HPM.

In addition, the present invention by using ozone instead of hydrogen peroxide, which is a traditional oxidant significantly improved the cleaning power for metal ions and produced an environmentally friendly cleaning composition.

Claims (3)

i) 3-5% by volume of 10% citric acid by organic acid; Ii) 3-7% by volume of 31% hydrogen peroxide or 1-150 ppm ozone as oxidizing agent; Iii) one or more additives selected from the group consisting of fluorine-based anionic surfactants, hydrofluoric acid and ammonium fluoride to prevent adsorption of particles; And Iii) residual ultrapure water; Semiconductor element cleaning composition containing The composition for cleaning a semiconductor device according to claim 1, wherein the fluorine-based anionic surfactant is a fluoroalkylsulfonamide compound. The composition for cleaning a semiconductor device according to claim 1 or 2, wherein the content of each additive is 10 to 1000 ppm of fluorine-based anionic surfactant, 10 ppm to 250 ppm of 49% hydrofluoric acid, and 10 to 500 ppm of ammonium fluoride.

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