JP3415451B2 - Determination of trace metal elements - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for quantifying a trace amount of metal element for quantifying an ultratrace amount of metal element contained in a polymer resin containing organosilicon such as polysilane and siloxane.

[0002]

2. Description of the Related Art Conventionally, semiconductor devices (elements) have been required to have improved functions or increased capacities, but there has also been a demand for conflicting propositions of making semiconductor devices compact. In response to such demands, various technologies have been developed and promoted.

For example, in the manufacture of integrated circuits, polymer resins containing organic silicon such as polysilane and siloxane are used for patterning active elements. However, for organic silicon polymers, alkali metals,
If metallic impurities such as heavy metals are present (contained), even if the amount thereof is very small, it causes the breakdown voltage of the insulating oxide film and the PN junction leak. That is, the trace amount of metallic impurities contained in the organic silicon polymer resin used in the ULSI manufacturing process has an important influence on the functional reliability of the finally manufactured ULSI. Therefore, in this type of organic silicon polymer resin, it is desired to remove metal impurities as much as possible.

In response to the above requirements, the organic polymer sample 41 for semiconductors such as photoresist and epoxy resin is generally diluted with an organic solvent 42 in the procedure shown in FIG.
After the operation described above, the decomposition 43 is performed in about 5 minutes and the impurity elements in these resin samples are quantified by the graphite furnace atomic absorption method 44 or the like. Specifically, for example, aliphatic hydrocarbons, aromatic hydrocarbons, ethers, and ketones are preferably used, the organic polymer is dissolved in these organic solvents, and this resin solution is directly used in an ICP mass spectrometer or a graphite furnace. Quantitative analysis of trace metal elements using an atomic absorption spectrometer.

However, if an attempt is made to apply this method to an organosilicon polymer resin, not only the organic substances present in the resin but also silicon as a matrix will significantly affect the signals and absorbances of each element, and accurate quantification will be possible. There was a problem that it was difficult.

Furthermore, since the method of quantification using the above-mentioned organosilicon polymer resin solvent is based on dilution,
The detection sensitivity of alkali metal elements and heavy metal elements is still poor,
For example, the concentration of each metal-based impurity is 0. It is difficult to measure at 1 ppm or less, and there is a limit to the current extremely high-purity organosilicon polymer resin due to its poor detection sensitivity.

[0007]

The conventional method for analyzing a trace amount of metal elements is such that silicon existing as an impurity in the organosilicon polymer resin interferes with the measurement, so that the concentration of each metal-based impurity element is 0.001 ppm level. It was not possible to measure with high sensitivity.

The present invention has been made in order to solve the above problems, and is for a manufacturing process of a semiconductor device capable of measuring the concentration of each metallic impurity element in an organosilicon polymer resin with high sensitivity of 0.001 ppm level. It is an object of the present invention to provide a method for analyzing an ultratrace amount of metal elements in a high-purity organosilicon polymer resin suitable for such purposes.

[0009]

In order to achieve the above object, a method for determining a trace amount of a metal element according to claim 1 comprises an oxidation step of converting silicon contained in a polymer resin containing organosilicon into silicon dioxide, and The method comprises a silicon dioxide removing step of separating silicon dioxide from the polymer resin, and a quantifying step of quantifying residual metal impurities by decomposing and removing the polymer resin with an organic substance decomposing solvent containing at least one oxidizing acid. And

According to a second aspect of the present invention, there is provided a method for quantifying a trace amount of a metal element according to the first aspect, wherein the oxidizing step is sulfuric acid, hydrogen peroxide,
The method is characterized in that the method is selected from nitric acid, potassium permanganate, potassium periodate, periodate, ozone water, and an oxidation action utilizing ultraviolet absorption.

The method for quantifying trace metal elements according to claim 3 is characterized in that in claim 2, the sulfuric acid is an acid adjusted to a range of 1% to 20% . Furthermore, the sulfuric acid
More preferably, it is in the range of 3% -7%. Claim 4
Determination method of trace metal elements, in claim 1, wherein
The oxidizing acid is characterized by being selected from sulfuric acid, nitric acid, perchloric acid, hydrochloric acid and hydrofluoric acid.

A method for quantifying a trace metal element according to claim 5 is the method according to claim 1, wherein the organic silicon-containing polymer resin is selected from polysilane, polysilane polymer, polysilane derivative, siloxane, siloxane polymer, and siloxane derivative. It is a resin.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION The method for analyzing an ultratrace amount of metal elements in an organosilicon polymer resin according to the present invention uses an organic silicon polymer resin containing impurities in a protic solvent to convert silicon into silicon dioxide. The method is characterized by comprising a step, a step of separating the formed silicon dioxide while preventing impurities from entering, and a step of decomposing and removing an organic substance with an oxidizing acid to quantify a residual metal impurity.

The present invention has diligently studied and studied a method for removing and reducing a small amount of metal impurities contained in a resin for electronic parts such as an organic silicon polymer resin, and as a result, treatment with an oxidizing acid or the like has been conducted. When applied, it is based on the finding that the silicon dioxide in the resin separates and can be removed. Utilizing this phenomenon, the metal impurity element concentration in each resin is 0.001 ppm level compared to the conventional
It was made based on the finding that it is 100 times more sensitive and can be easily and reliably quantified.

In the present invention, the polymer resin containing an organic silicon containing an impurity to be treated may be an organic silicon polymer resin produced by any conventionally known method. For example, polysilanes may be used. , Those obtained by reacting a polyvalent halosilane with an alkali metal or the like, which is the most general synthetic method of polysilane, are used, and polysilanes represented by the general formula (Formula 1) are particularly preferably used. .

[0016]

[Equation 1] As the siloxanes, the siloxanes represented by the formula 2 are preferably used.

[0017]

[Equation 2]

The impurities contained in the organosilicon polymer resin are, for example, sodium (Na), potassium (K), iron (Fe), copper (Cu), calcium (C).
a), magnesium (Mg) and the like, and among these metal impurities, for example, iron (2+ or 3+), sodium (1+), potassium (1+), copper (1+ or 2).
+), Calcium (2+), and magnesium (2+) are displayed as ions.

In the present invention, it is necessary that the acid, solvent, etc. used have the highest possible purity, and as the impurity concentration of the contained metal, iron and copper: 0.1 ppb or less, calcium and magnesium: 0.05 ppb or less. , Sodium and potassium: 0.01 ppb or less is desirable. Regarding the temperature condition in the case of using an acid during the required decomposition treatment, the higher the temperature is, the more the reaction effect is improved. Therefore, the effectiveness is exhibited by treating the temperature at 50 ° C. or higher, preferably 70 ° C. or higher. It is necessary to set the upper limit temperature in a range that does not cause thermal decomposition of the resin to be treated, and it is generally preferable to set the upper limit to 20 ° C. or lower than the thermal decomposition temperature of the resin to be treated. The amount of the oxidizing agent used is not particularly limited, but from the viewpoint of achieving a more sufficient effect and minimizing the contamination from the reagent, it is selected within a range of 10 times the capacity of the resin to be treated or less. Preferably. In the present invention, in order to avoid becoming a new pollution source such as a device (container or instrument) used in a series of operations such as a resin decomposition process, a separating device, a drying device, a material from which impurities are not eluted, such as Teflon or Of course, synthetic quartz (or a structure coated with these) is used, and the working environment (atmosphere) is taken into consideration. The protic solvent used in the oxidation step for oxidizing the contained silicon is 1% -20% sulfuric acid, 35% hydrogen peroxide, 30-68% nitric acid, potassium permanganate, potassium periodate, periodic acid. , Or at least one of the wavelengths utilizing ultraviolet absorption or ozone water.

In the method according to the present invention, an organosilicon polymer resin containing impurities such as sodium and potassium is first brought into contact with dilute sulfuric acid, and silicon dioxide is separated by hydrolysis. Generally, silicon dioxide can be removed as silicofluoride by the reaction of SiO2 + 6HF → H2SiF6 + 2H2O. Also,
At this time, if Si remains, it can be similarly removed as silicon dioxide by the reaction of Formula 3 with nitric acid + hydrofluoric acid system.

[0021]

[Equation 3]

Hydrocarbons, aromatic hydrocarbons and the like remain in the solution after this treatment, but these resins can be easily decomposed by oxidizing acids such as nitric acid and sulfuric acid, so that the desired metal impurities can be obtained. Only remains in solution.

As a result of the above-mentioned treatment, the peaks due to Si and organic substances, which remained as a matrix before separation and interfered with the measurement, were reduced, and the target element peaks were clearly detected. As described above, by using this method, it became possible to quantify the impurity element with a sensitivity 10 to 100 times higher than that of the conventional method.

[0024]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows a flow chart for carrying out the analysis method according to the present invention. The present invention is not limited to the following examples. In each example, Me is a methyl group, Ph is a phenyl group, and Mn is
Is the number average molecular weight, and Mw is the weight average molecular weight.

(Example 1) (MePhsi) n (M) of polysilanes obtained by reacting sodium with methylphenyldichlorosilane in a toluene solvent under reflux.
n23000, Mw 97000) 10 g of toluene 19
It was dissolved in 0 g.

1 ml of this polysilane solution was placed in a Teflon container, 10 ml of 5% sulfuric acid was further added, and hydrolysis was carried out for 1 hour while maintaining the temperature at 100 ° C. Then, silicon dioxide was deposited on the surface. The process up to this point is the oxidation step of converting silicon contained in the polymer resin containing organosilicon into silicon dioxide.

Nitric acid + hydrofluoric acid (1: 1) was added to this solution.
5 ml of the mixed solution was added, and the mixture was decomposed at 230 ° C. for 30 minutes. This step is a silicon dioxide removal step of separating the silicon dioxide from the polymer resin. It is characterized by having.

Next, 5 ml of a mixed solution of nitric acid + perchloric acid (1: 1) was added, and the mixture was heated and decomposed at 230 ° C. until almost all the solution was evaporated. After this, the solution became a transparent solution (this transparency serves as an index for removing organic substances). The obtained sample solution was applied to a Zemann atomic absorption spectrometer (Perkin-Elmer: 5100ZL) to analyze Na, K, Fe, Cu and Al.
The above steps are the quantitative steps of decomposing and removing the polymer resin with an oxidizing acid to quantify the residual metal impurities. The measurement conditions in the Zemann atomic absorption spectrometer are as follows. Drying: 120
C, 30 seconds. Ashing: 600 ° C for Na, 700 ° C for K, F
e, Cu and Al at 1000 ° C. for 30 seconds each. Atomization: 2500 ° C. for Na, 2700 ° C. for K, 2800 ° C. for Fe, Cr, and Al for 4 seconds each. Carrier gas: 300 ml / min with argon, but not flow during atomization. Measurement wavelength: Na is 589.0 nm, K is 766.
5 nm, Fe is 248.3 nm, Cr is 324.8 n
m and Al are 309.3 nm. FIG. 2 shows the measured wavelength intensity of Fe at 248.3 nm, and the peak output result was obtained and could be quantified. It was possible to quantify other atoms as well.

As a result of the above, Na: 5 ppb, K: 3 p
pb, Fe: 8 ppb, Cu: 7.5 ppb, Al: 1
It was 0 ppb. Comparative Example 1 Polysilane of the same type as the polysilane used in Example 1 was analyzed by a conventional flow chart shown in FIG. 4 in which silicon was measured without removing silicon as an oxide. The result was measured for the absorption wavelength of Fe at 248.3 nm as in FIG. 2, and is FIG. The measurement was difficult due to the interference of the silicon matrix.

(Example 2) This example is different from Example 1 in that a siloxane-based resin is used as an organic silicon polymer resin containing impurities as an object to be measured.

First, 51 g of dimethyldichlorosilane and 0.3 g of aluminum chloride as a catalyst were placed in a reaction vessel equipped with a stirrer, a thermometer, and a reflux cooling device.
33 g of 4-biphenyldimethylsilane was dropped into this system from a dropping funnel at 15 to 20 ° C. over 2 hours to obtain a reaction liquid. 0.4 g of anisole was added to the reaction solution to deactivate the aluminum chloride, and then disilane-containing organopolysiloxane was obtained by distillation.

In the same manner as in Example 1, 1 ml of this siloxane solution was placed in a Teflon container, 10 ml of 5% sulfuric acid was further added as a proton-generating agent, and hydrolysis was carried out for 1 hour while maintaining the temperature at 150 ° C. Then, silicon dioxide was deposited on the surface. Up to this point is the oxidation step.

Nitric acid + hydrofluoric acid (1: 1) was added to this solution.
10 ml of the mixed solution was added, and the mixture was decomposed at 230 ° C. for 1 hour.
This process is a silicon dioxide removal process. Next, 5 ml of a mixed solution of nitric acid + perchloric acid (1: 1) was added, and the mixture was heated and decomposed at 230 ° C. until the solution was almost evaporated. After this time, the solution became a clear solution. The obtained sample solution was applied to a Zeman atomic absorption spectrometer (Perkin-Elmer: 5100ZL) to obtain Na,
Analysis of K, Fe, Cu and Al was performed. As a result, N
a: 10 ppb, K: 2 ppb, Fe: 3 ppb, C
It was possible to quantify with Al: 5 ppb as u: 1 ppb.

(Comparative Example 2) The siloxane of the same type as the siloxane used in Example 1 is the same as that of Example 2 except that the flow chart shown in FIG. 4, that is, the step of removing silicon by oxide is not taken. Then, the analysis was performed. As a result, the measurement was difficult due to the interference of the matrix as in Comparative Example 1.

Example 3 1 ml of a solution of polysilane (MePhSi) n (Mn23000, MW97000) obtained by the same operation as in Example 1 was placed in a Teflon container, 10 ml of 5% sulfuric acid was added, and the mixture was heated to 100 ° C. Hydrolysis was carried out for 1 hour while maintaining the temperature. After silicon dioxide was deposited on the surface, 5 ml of a mixed solution of nitric acid and hydrofluoric acid (1: 1) was added and decomposed at 230 ° C. for 30 minutes. Next, nitric acid + perchloric acid (1: 1) mixed solution 5m
1 was added thereto, and the mixture was decomposed by heating at 230 ° C. until the solution was almost evaporated.

The obtained sample solution was applied to a heat vaporization ICP mass spectrometer (Seiko Denshi Kogyo: SPS8000) to obtain Fe, N
The analysis of i, Al and Cu was carried out. Drying stage: 100 ℃, 60
Seconds. Drying stage 2: 200 ℃ for 30 seconds. Ashing: 400 ° C, 30 seconds.
Vaporization: 2300 ° C, 5 seconds. Measured mass number is 27Al, 56Fe, 63Cu, 59N
i was used. As a result, Al: 10ppb, Fe: 8pp
b, Cu: 7 ppb, Ni: 2 ppb.

Comparative Example 3 Polysilane of the same type as the polysilane used in Example 1 was analyzed according to the flow chart shown in FIG. It was difficult to measure 28Al for 28Al and 56Si for 28Fe28Si for 56Fe, and other elements were also disturbed by the organic matrix.

(Examples 4 to 15) The following Examples 4 to 15
Shows that the protic solvent used in the oxidation step in Example 1 was variously changed from sulfuric acid to other chemicals, and the other steps were the same, and metal impurities were measured. Table 1 summarizes the protic solvent, measurement conditions, measurement results, and the like.

[0039]

[Table 1]

As is clear from Table 1, hydrogen peroxide, nitric acid, potassium permanganate, potassium periodate, periodic acid and ozone water can be used as the protic solvent, and the ultraviolet absorption It has been found that the same effect as the use of a protic solvent can be expected by utilizing the oxidation effect utilizing the. Further, sulfuric acid is desirable in that it is an acid prepared in the range of 1% to 20%, and particularly desirably in the range of 3% to 7%.

[0041]

As described above, according to the first and second inventions of the present application, it has become possible to rapidly decompose an organosilicon polymer resin, which has been difficult in the past, and to supply a decomposition solution with low contamination. It was Therefore, according to the method of the present invention, the organosilicon polymer resin can be decomposed with high efficiency as compared with the conventional method and apparatus.

[Brief description of drawings]

FIG. 1 is a flowchart showing a method for analyzing an organosilicon polymer resin of the device of the present invention.

FIG. 2 is a diagram showing a background absorption peak in an atomic absorption method according to Example 1 of the present invention.

FIG. 3 Background absorption peak in conventional atomic absorption method

FIG. 4 is a flowchart showing a conventional method for analyzing an organosilicon polymer resin.

[Explanation of symbols]

1 sample 2 heating process 3 oxidation process 4 Oxide removal process 5 Evaporative drying process 6 Graphite furnace atomic absorption spectrometry

─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-7-72056 (JP, A) JP-A-9-26401 (JP, A) JP-A-9-8088 (JP, A) JP-A-8- 152385 (JP, A) JP 7-333116 (JP, A) JP 9-257669 (JP, A) JP 9-82769 (JP, A) JP 9-145569 (JP, A) (58) Fields surveyed (Int.Cl. ⁷ , DB name) G01N 1/00-1/34 G01N 31/00 G01N 33/44

Claims (5)

(57) [Claims] 1. An oxidation step for converting silicon contained in a polymer resin containing organosilicon into silicon dioxide, a step for removing silicon dioxide for separating the silicon dioxide from the polymer resin, and a step for oxidizing the polymer resin with an oxidizing acid. A method for quantifying a trace amount of a metal element, comprising a quantification step of decomposing and removing and quantifying a residual metal impurity. 2. The oxidation step is a method of selecting from sulfuric acid, hydrogen peroxide, nitric acid, potassium permanganate, potassium periodate, periodic acid, ozone water, and an oxidizing action utilizing ultraviolet absorption. The method for quantifying a trace metal element according to claim 1, wherein 3. The method for quantifying trace metal elements according to claim 2, wherein the sulfuric acid is an acid adjusted to a range of 1% -20% . 4. The oxidizing acid is sulfuric acid, nitric acid, perchloric acid,
The method for quantifying trace metal elements according to claim 1, wherein the method is selected from hydrochloric acid and hydrofluoric acid. 5. The trace metal according to claim 1, wherein the polymer resin containing organic silicon is a resin selected from polysilane, polysilane polymer, polysilane derivative, siloxane, siloxane polymer, and siloxane derivative. Quantitative method of elements.