JP2001345301A - Method of cleaning electronic material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of cleaning an electronic material of highly general purpose by which both metals and fine particles can be effectively removed from an object to be cleaned in a short time and at a low cost, without using a dense chemical liquid or chemicals designated as poisonous substance during a cleaning step after CMP. SOLUTION: This method is used for cleaning an electronic material to which CMP is applied in advance, and a cleaning liquid is ultrapure water of 45 deg.C or higher in which hydrogen, an oxygen or a rare gas is melted. The cleaning liquid is used to clean the electronic material while irradiating an ultrasonic wave of 10 kHz to 3 MHz to the cleaning liquid.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for cleaning electronic materials. More specifically, the present invention relates to CMP (Chemical Mechanical Polishing, Chemical Mechanical P
The present invention relates to a method for cleaning an electronic material, which can remove metal impurities and fine particles such as a residual abrasive adhered to the surface of the electronic material after the polishing simultaneously and effectively by wet cleaning.

[0002]

2. Description of the Related Art Conventionally, in the cleaning process of the semiconductor industry, wet cleaning called RCA cleaning has been mainly used. RCA cleaning is performed using a mixture of sulfuric acid and hydrogen peroxide (SP
M) is heated to 120 to 150 ° C., a mixture of ammonia and hydrogen peroxide (APM) is heated to 60 to 80 ° C., or a mixture of hydrochloric acid and hydrogen peroxide is used. This is a cleaning method in which (HPM) is heated to 60 to 80 ° C. and used. If this cleaning method is adopted, the cost of chemicals, the cost of ultrapure water for rinsing, the cost of waste liquid treatment, the cost of air conditioning that exhausts chemical vapors and creates clean air, etc. are reduced, and the use of large amounts of water is reduced. Mass disposal of chemicals,
In order to reduce the load on the environment such as emission of exhaust gas, the wet cleaning process has recently been reviewed. Also,
In recent years, in the semiconductor industry, wiring is integrated on a wafer in order to improve the degree of integration. It is necessary to planarize an oxide film (insulating film) in order to perform multilayer wiring, and CMP has been adopted in a semiconductor device manufacturing process as a technique for that. In this CMP step, polishing is performed using a polishing liquid in which polishing particles such as silica (SiO ₂ ) are dispersed in a solution containing potassium such as an aqueous potassium hydroxide (KOH) solution. However, chemical vapor deposition (CVD,
Chemical Vapor Deposition
When the oxide film deposited by the above method is polished using the above-mentioned polishing liquid, the problem that potassium (K) tends to remain on the wafer has become apparent. If potassium remains on the wafer, it must be removed by cleaning because it affects device characteristics. Further, since fine particles of the abrasive remain on the wafer, they need to be removed by cleaning. Conventional cleaning after CMP generally involves a plurality of cleaning steps in order to remove metals such as potassium and fine particles. For example, (1) ultrapure water rinse → brush scrub cleaning → APM + ultrasonic → ultrapure water rinse → HF → ultrapure water rinse → drying, (2) warm ultrapure water →
APM + ultrasonic wave → first ultrapure water rinse → second ultrapure water rinse → drying, (3) brush scrub cleaning → HF → ultrapure water rinse → drying etc. (1), (2)
The method of (1) has a problem that a large amount of a chemical solution is used, a large amount of chemical vapor is generated, a large amount of ultrapure water is used for rinsing, productivity is low, and a number of cleaning steps are required. Further, the methods (1) and (3) have a problem that a huge cost is required for waste liquid treatment because a hydrofluoric acid waste liquid regulated by the Poison Control Law is generated.

[0003]

DISCLOSURE OF THE INVENTION The present invention is an object of the present invention is to provide a method for cleaning metal and fine particles simultaneously, in a short time, at low cost, without using a concentrated chemical solution or a chemical which has been designated as a toxicant in a cleaning step after CMP. An object of the present invention is to provide a highly versatile method for cleaning electronic materials that can be removed from an object to be cleaned.

[0004]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to solve the above-mentioned problems, and as a result, they have been found to adhere to the CVD oxide film by cleaning with warm ultrapure water heated to 45 ° C. or more. It has been found that potassium can be easily removed, and furthermore, by dissolving a gas such as hydrogen in ultrapure water, metal impurities such as potassium and fine particles can be removed at the same time. Was completed. That is, the present invention relates to (1) a method for cleaning an electronic material after performing CMP, wherein ultrapure water at 45 ° C. or higher in which hydrogen, oxygen, or a rare gas is dissolved is used as a cleaning liquid, and the cleaning liquid has a frequency of 10 kHz to 3 MHz. And (2) the method for cleaning an electronic material according to claim 1, wherein an alkali is added to the cleaning solution. . Further, as preferred embodiments of the present invention, (3) the method for cleaning an electronic material according to (1), wherein the dissolved gas concentration of hydrogen, oxygen, or a rare gas is 50% or more of the saturation solubility; , Ammonia or tetramethylammonium hydroxide
And a method for cleaning an electronic material described in the section.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION A method for cleaning an electronic material according to the present invention comprises:
This is a method of cleaning an electronic material after performing CMP, in which ultrapure water at 45 ° C. or higher in which hydrogen, oxygen, or a rare gas is dissolved is used as a cleaning liquid. If the temperature is lower than 45 ° C., a sufficient cleaning effect cannot be obtained. From the viewpoint of the cleaning effect, the temperature is preferably 60 ° C. or higher, more preferably 80 ° C. or higher. According to the method of the present invention, the C
It can be particularly suitably applied to cleaning of a semiconductor substrate on which MP has been performed. As the CVD oxide film, for example, P-TE
OS (Plasma enhanced tetraet)
hyorthoslicate) oxide film, BPSG
(Boron-doped phospho-sili
Cat Glass (Oxide), NSG (Non-do)
ped silica glass) Oxide film, TMS
(Plasma enhanced tetrametry
oxysilane) oxide film and the like. Since a polishing liquid containing an alkali such as potassium hydroxide and fine particles such as silica, ceria, and alumina is used for the CMP of the electronic material, the surface of the electronic material after the CMP contains potassium derived from the polishing liquid. Metal impurities and fine particles such as silica. When the temperature of ultrapure water in which hydrogen, oxygen, or a rare gas is dissolved is 45 ° C. or higher, metal impurities attached to the surface of the electronic material can be effectively removed.

In the method of the present invention, there is no particular limitation on the method for producing ultrapure water at 45 ° C. or higher in which hydrogen, oxygen or a rare gas is dissolved. For example, hydrogen, oxygen or Noble gas can be dissolved, or
Ultrapure water in which hydrogen, oxygen, or a rare gas is dissolved can be heated to 45 ° C. or higher. In the method of the present invention, the concentration of hydrogen, oxygen or a rare gas in the cleaning solution is not particularly limited, but the dissolved gas concentration is preferably 50% or more of the saturation solubility at the temperature of the cleaning solution, and is preferably 75% or more. Is more preferred. Incidentally, the saturated solubility in water at 60 ° C. was 1.43 mg / L for hydrogen and 27.9 mg / oxygen for oxygen.
L, helium 1.59 mg / L, neon 8.51 mg / L, argon 37.0 mg / L, krypton 123 mg / L, xenon 293 mg / L. Hydrogen, oxygen or noble gas is 1
The seed alone can be dissolved in ultrapure water, or
A combination of more than one species can be dissolved in ultrapure water.
There is no particular limitation on the method of producing ultrapure water in which hydrogen, oxygen or a rare gas is dissolved used in the method of the present invention, but the ultrapure water is degassed in advance to reduce the degree of saturation of the dissolved gas, and the gas dissolution capacity in water is reduced. It is preferable to dissolve hydrogen, oxygen or a rare gas after making an empty space. When dissolving hydrogen, oxygen, or a rare gas, gas-permeable membrane modules can be used in multiple stages to remove dissolved gas and dissolve hydrogen, oxygen, or a rare gas. For example, a gas permeable membrane module is provided in two stages, a reduced-pressure membrane degassing is performed on all dissolved gases using the gas permeable membrane module in the preceding stage, and hydrogen, oxygen or a rare gas is used in the gas permeable membrane module in the subsequent stage. Can be dissolved. A gas permeable membrane module is provided in two stages, and decompression membrane degassing for all dissolved gases and dissolution of hydrogen, oxygen, or a rare gas are performed in two stages, so that hydrogen, oxygen, or a rare gas is wastefully released. Without being dissolved, it can be almost quantitatively dissolved in ultrapure water.

In the method of the present invention, the pH can be adjusted to 7 or more by adding an alkali to ultrapure water in which hydrogen, oxygen or a rare gas is dissolved. By adding the alkali, the effect of removing fine particles such as abrasives attached to the wafer surface and the effect of preventing re-adhesion can be enhanced. The alkali used for pH adjustment is not particularly limited. For example, ammonia, sodium hydroxide, potassium hydroxide, tetramethylammonium hydroxide (TMA
H) and the like. Among them, high-purity aqueous ammonia and tetramethylammonium hydroxide can be preferably used. In the method of the present invention, the CM
There is no particular limitation on the method of cleaning the electronic material after performing P with ultrapure water in which hydrogen, oxygen or a rare gas is dissolved as a cleaning liquid. For example, a method in which the electronic material is immersed in a water tank filled with the cleaning liquid and batch-cleaned. Processing can be performed, or single-wafer cleaning in which an electronic material is placed on a spinner or a loader and a cleaning liquid is poured in a radial direction from the center of the electronic material to perform the processing can be performed. In the method of the present invention, it is necessary to irradiate ultrasonic waves when cleaning an electronic material using ultrapure water at 45 ° C. or higher in which hydrogen, oxygen or a rare gas is dissolved as a cleaning liquid. Irradiation of ultrasonic waves can enhance the effect of removing fine particles such as abrasives. The ultrasonic wave to be irradiated has a frequency of 10 kHz to 3 MHz, preferably 0.8 M
Hz to 1.6 MHz. If the frequency of the ultrasonic wave is less than 10 kHz, there is a possibility that the cavitation effect may damage an extremely finely processed electronic material. When the frequency of the ultrasonic wave exceeds 3 MHz, cavitation does not occur and the cleaning effect is not recognized. According to the method for cleaning an electronic material of the present invention, metal impurities such as potassium and fine particles such as a residual abrasive adhered to the surface of the electronic material after the CMP are simultaneously performed in a short time by one-step cleaning. Can be removed.

[0008]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, which should not be construed as limiting the present invention. In Examples and Comparative Examples, a 6-inch wafer with a P-TEOS film was used as the wafer with a CVD oxide film. The potassium concentration on the wafer after the CMP step and after the cleaning was measured using a total reflection X-ray fluorescence analyzer [Rigaku Corporation, TXRF3750].
The number of fine particles can be measured using a laser scattering particle inspection device [Topcon
Using WM-1500], the fine particles having a particle size of 0.20 μm or more were counted. For cleaning the wafer, a spin cleaning machine [Kanamex Corporation, WSC-200MS] was used, and an ultrasonic wave application nozzle [Honda Electronics Co., Ltd., Pulse Jet W-3]
57P25-AHPF] to irradiate an ultrasonic wave of 1.0 MHz. Example 1 60 supplied from a hot ultrapure water supply device [Kurita Kogyo Co., Ltd.]
Using ultra-pure water at a temperature of ℃ as raw water, hydrogen is dissolved in a hydrogen water production system using a membrane dissolution method [Kurita Kogyo Co., Ltd.], and the dissolved hydrogen concentration is 1.
Produce 2 mg / L hydrogen water, send it to the spin washer,
The wafer was spray-cleaned while being irradiated with ultrasonic waves. The potassium concentration on the wafer before cleaning was 43.2 × 10 ¹⁰ atoms / cm ² , and the number of fine particles exceeded the upper limit of measurement of 5,500 particles / wafer. By cleaning with a cleaning liquid flow rate of 1 L / min and a cleaning time of 30 seconds, the potassium concentration on the wafer is 7.21 × 10 ¹⁰
The number of atoms / cm ² and the number of fine particles were 57 / wafer. Example 2 Washing was carried out in the same manner as in Example 1 using a washing solution adjusted to pH 9.4 by adding 1 mg / L of ammonia to hydrogen water having a temperature of 60 ° C. and a dissolved hydrogen concentration of 1.2 mg / L. Was. The potassium concentration on the wafer was reduced from 49.1 × 10 ¹⁰ atoms / cm ² to 9.33 × 10 ¹⁰ atoms / cm ² and the number of fine particles was 5.5
It was reduced from more than 00 wafers / wafer to 36 wafers / wafer. Example 3 The cleaning was performed in the same manner as in Example 1 except that the cleaning time was set to 60 seconds. The potassium concentration on the wafer is 40.2 ×
The number of particles decreased from 10 ¹⁰ atoms / cm ² to the lower limit of detection of 3.11 × 10 ¹⁰ atoms / cm ² or less, and the number of fine particles decreased from 5,500 particles / wafer or more to 21 particles / wafer. Example 4 The cleaning was performed in the same manner as in Example 2 except that the cleaning time was changed to 60 seconds. The potassium concentration on the wafer was 41.3 × 1
The particle number was reduced from 0 ¹⁰ atoms / cm ² to 3.11 × 10 ¹⁰ atoms / cm ² or less, and the number of fine particles was reduced from 5,500 particles / wafer or more to 17 particles / wafer.

Example 5 The temperature of ultra pure water was set to 80 ° C., and the dissolved hydrogen concentration was 0.8 mg /
The cleaning was performed in the same manner as in Example 1 except that L hydrogen water was produced. The potassium concentration on the wafer was 45.4 × 1
From 0 ¹⁰ atoms / cm ² to the lower limit of detection, 3.11 × 10 ¹⁰ atoms / cm ²
cm ² or less, and the number of fine particles was reduced from the upper limit of measurement of 5,500 particles / wafer to 29 particles / wafer. Example 6 Washing was performed in the same manner as in Example 5 except that the pH was adjusted to 9.4 by adding 1 mg / L of ammonia to hydrogen water.
The potassium concentration on the wafer is 42.2 × 10 ¹⁰ atoms / cm ²
From 3.11 × 10 ¹⁰ atoms / cm ² or less, and the number of fine particles decreased from more than 5,500 / wafer to 9 / wafer. Example 7 The cleaning was performed in the same manner as in Example 5, except that the cleaning time was changed to 60 seconds. The potassium concentration on the wafer was 43.8 ×
It is reduced from 10 ¹⁰ atoms / cm ² to 3.11 × 10 ¹⁰ atoms / cm ² or less, and the number of fine particles is increased from 5,500 particles / wafer or more to 16
Reduced to pieces / wafer. Example 8 The cleaning was performed in the same manner as in Example 6, except that the cleaning time was 60 seconds. The potassium concentration on the wafer was 46.5 × 1
From 0 ¹⁰ atoms / cm ² to 3.11 × 10 ¹⁰ atoms / cm ² or less, and the number of fine particles is from 5,500 / wafer or more to 5 /
Reduced to wafer.

Comparative Example 1 25 ° C. supplied from an ultrapure water production system [Kurita Kogyo Co., Ltd.]
Hydrogen is dissolved in ultra-pure water as raw water using a membrane-dissolved hydrogen water production system [Kurita Kogyo Co., Ltd.], and the dissolved hydrogen concentration is 1.2 m.
g / L of hydrogen water is produced, fed to a spin washer, and sprayed onto the wafer at a flow rate of 1 L / min while irradiating ultrasonic waves.
Washed for 0 seconds. Potassium concentration on wafer is 46.7x
The particle number was reduced from 10 ¹⁰ atoms / cm ² to 38.1 × 10 ¹⁰ atoms / cm ² , and the number of fine particles was reduced from the measurement upper limit of 5,500 or more / wafer to 77 / wafer. Comparative Example 2 Washing was carried out in the same manner as in Comparative Example 1 using a cleaning solution adjusted to pH 9.4 by adding ammonia 1 mg / L to hydrogen water having a temperature of 25 ° C. and a dissolved hydrogen concentration of 1.2 mg / L. Was. The potassium concentration on the wafer should be between 44.1 × 10 ¹⁰ atoms / cm ² and 3
7.5 × 10 ¹⁰ atoms / cm ² and the number of fine particles is 5,50
The number decreased from 0 / wafer to 45 / wafer. Comparative Example 3 80 supplied from a hot ultrapure water supply device [Kurita Kogyo Co., Ltd.]
Ultra-pure water at a temperature of 0 ° C. was fed to a spin washer, and was sprayed onto the wafer at a flow rate of 1 L / min while irradiating ultrasonic waves to wash for 60 seconds. Potassium concentration on wafer is 41.2 × 10 ¹⁰ atoms / c
was reduced from m ² to 3.11 × 10 ¹⁰ atoms / cm ² or less of the detection limit, 5 of both the measurement upper limit number of fine particles before and after washing,
More than 500 wafers / wafer. Comparative Example 4 Washing was performed in the same manner as in Comparative Example 3 except that the pH was adjusted to 9.4 by adding 1 mg / L of ammonia to 80 ° C. ultrapure water. Although the potassium concentration on the wafer was reduced from 45.7 × 10 ¹⁰ atoms / cm ² to 3.11 × 10 ¹⁰ atoms / cm ² or less, the number of fine particles before and after cleaning was 5,500, which is the upper limit of the measurement.
Pcs / wafer or more. Examples 1 to 8 and Comparative Examples 1 to
Table 1 shows the results of No. 4.

[0011]

[Table 1]

As shown in Table 1, in Examples 1 to 8 in which hot ultrapure water at 60 ° C. or 80 ° C. in which hydrogen was dissolved was used as a cleaning liquid, potassium and fine particles on the wafer were both removed. To which hydrogen was dissolved
In Comparative Examples 1 and 2 using ultrapure water at a temperature of 80 ° C. as cleaning liquids, fine particles were removed but the removal rate of potassium was extremely low, and Comparative Examples 3 and 4 using warm ultrapure water at 80 ° C. in which hydrogen was not dissolved were used. In No. 4, potassium was removed, but fine particles were not removed. Further, from the results of Examples 1 to 8, it is found that the removal rate of fine particles can be improved by irradiating ultrasonic waves during cleaning, and the removal of fine particles can also be achieved by adjusting the pH to 9.4 by adding ammonia. Rate is improved,
It can be seen that extending the washing time from 30 seconds to 60 seconds also improves the removal rate of fine particles, and increasing the water temperature improves both the removal rate of potassium and the removal rate of fine particles. From the results of Comparative Examples 1 to 4, by washing with hot ultrapure water as a washing liquid and then washing with hydrogen water as a washing liquid, or washing with hydrogen water as a washing liquid and washing with hot ultrapure water as a washing liquid, potassium on the wafer was removed. It is presumed that both of the fine particles can be removed, but such a washing method is not advantageous because it requires twice the amount of water and twice the washing time as the method of the present invention.

[0013]

According to the method for cleaning an electronic material of the present invention,
Metal impurities such as potassium and fine particles such as abrasive remaining on the surface of the electronic material after the CMP can be simultaneously removed in a short time by one-step cleaning.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) B08B 3/12 B08B 3/12 A

Claims (2)

[Claims] 1. A method of cleaning an electronic material after performing CMP, wherein ultrapure water of 45 ° C. or higher in which hydrogen, oxygen or a rare gas is dissolved is used as a cleaning liquid, and ultrasonic waves of 10 kHz to 3 MHz are applied to the cleaning liquid. A method for cleaning electronic materials, wherein the cleaning is performed while irradiating. 2. The method for cleaning an electronic material according to claim 1, wherein an alkali is added to the cleaning liquid.