JPH0558789A - Production of silicone single crystal by chemical vapor phase growing method and fractional determination of ultramicro-element in chlorosilane as its raw material and in silicon single crystal produced - Google Patents

Abstract

PURPOSE:To provide a producing method of a silicon single crystal for semiconductor by chemical vapor phase growing method and a fractional determination method of ultramicro-elements such as phosphorus, arsenic, boron and aluminium in the silicon single crystal and in a chlorosilane which is raw material when producing the silicon single crystal. CONSTITUTION:Hydrogen chloride gas and silicon formed by mixing at least one kind of chlorosilane gas selected from dichlorosilane, trichlorosilane, tetrachlorosilane and hydrogen at high temp. are fed to a seed-bar of the silicone single crystal to make the silicon single crystal for semiconductor grow while etching the surface of the silicon single crystal with hydrogen chloride gas. Later beam having 3100-3358mW/cm<2> energy on the irradiating surface is irradiated on the silicon single crystal and light emission spectrum is measured photoelectrically to determine quantitatively ultramicro-elements in the silicon single crystal. And, from the amount of the ultramicro-elements, an amount of the ultramicro-elements in the chlorosilane gas is converted.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a silicon single crystal for semiconductors by a chemical vapor deposition method, and ultratrace elements (phosphorus, arsenic, boron,
Aluminum and the like) and a method for fractionating and quantifying ultratrace elements in manufactured silicon single crystals.

[0002]

2. Description of the Related Art In order to produce silicon single crystals for semiconductors by chemical vapor deposition, silicon polycrystal seeds are used as a solid phase, and chlorosilanes or monosilane as a raw material are heated with a reducing component such as hydrogen. And then supply while reducing
A silicon polycrystal is grown on a seed of the silicon polycrystal, the grown silicon polycrystal is sampled, and a silicon single crystal is obtained by the zone floating method (FZ method). A semiconductor is manufactured using this silicon single crystal as a wafer.

In the silicon single crystal thus obtained, the ultratrace elements such as phosphorus, arsenic, boron and aluminum contained in the chlorosilanes used as raw materials exist as impurities as they are, It is a major factor in determining the electrical characteristics of semiconductors. Therefore, accurate fractional quantification of the ultratrace element in the silicon single crystal leads to quantification of the ultratrace element in the raw material and also becomes a factor to know the electrical characteristics of the semiconductor.

As a method of measuring the amount of trace elements in silicon crystals for semiconductors, American Society for Testing and Materials, F574.
The -83 method is known. In this method, a silicon polycrystal is manufactured by a chemical vapor deposition method, a silicon single crystal is obtained from the silicon polycrystal by a zone-floating method, the resistivity is measured, and then the zone-floating method is further performed in vacuum. Are repeated several times to remove the donors (phosphorus and arsenic), and the resistivity is measured again to calculate the total concentration of the remaining acceptors (boron and aluminum). The total concentration of phosphorus and arsenic can be calculated from the total concentration of phosphorus and arsenic from the difference in resistivity by calculating the difference between the resistivity measured previously and the resistivity measured later.

However, in the method for producing a silicon single crystal which is a combination of the conventional chemical vapor deposition method and the zone-floating method described above, there is contamination from the zone-floating apparatus and a sufficiently high purity is required. It was difficult to get. In addition, the band floatation method is also problematic in that the operation is complicated, requires skill, and takes a long time.

Further, the above-mentioned conventional method for measuring the amount of trace elements has the following drawbacks and is not suitable for quantitative determination of ultra-trace elements which requires highly accurate measurement. The concentration of the ultratrace element in the silicon polycrystal produced by the chemical vapor deposition method may vary depending on each crystal of the silicon polycrystal. When such a silicon polycrystal is continuously single-crystallized by the zone-floating method, the concentration of the ultratrace element in the silicon polycrystal, which is subsequently single-crystallized, is contained in the previously single-crystallized silicon polycrystal. It will be affected by the concentration of trace elements. Further, phosphorus, arsenic, and boron segregate toward the zone float method, so the actual concentration must take into consideration the effect of segregation. Further, when measuring the resistivity, if the amount of the ultratrace element is considerably small, the resistivity becomes large, and if it exceeds about 5000 Ω · cm, Joule heat is generated and an error occurs in the measured value. The calculated amounts of trace elements are not the concentration of each element, but only the total concentration of phosphorus and arsenic and the total concentration of boron and aluminum.

[0007]

The present invention has been made to solve the above-mentioned problems, and directly produces a silicon single crystal for semiconductors by a chemical vapor deposition method without using a zone-floating-fusing method. The purpose is to provide a method. In addition, ultra-trace elements (phosphorus, arsenic, boron, aluminum, etc.) in silicon single crystals produced by chemical vapor deposition, and ultra-trace elements in chlorosilanes used as raw materials for producing silicon single crystals. (Phosphorus, arsenic, boron,
The present invention provides a method for separately quantifying aluminum).

[0008]

The method for producing a silicon single crystal by the chemical vapor deposition method of the present invention, which has been made to achieve the above-mentioned object, comprises at least one selected from dichlorosilane, trichlorosilane and tetrachlorosilane.
Hydrogen chloride gas and silicon produced by mixing different types of chlorosilane gas and hydrogen gas at high temperature are supplied to a silicon single crystal seed rod, and the silicon single crystal is etched while etching the surface of the silicon single crystal with hydrogen chloride gas. Let it grow.

The method for fractionating and quantifying ultratrace elements (phosphorus, arsenic, boron, aluminum, etc.) in a silicon single crystal according to the present invention is a method for quantifying the energy of an irradiated surface of a silicon single crystal produced by chemical vapor deposition. Is 3100-335
An ultratrace element in a silicon single crystal is quantified by irradiating a laser beam of 8 mW / cm ² and photoelectrically measuring the emitted spectrum.

Further, the method for fractionating and quantifying ultratrace elements (phosphorus, arsenic, boron, aluminum, etc.) in chlorosilane gas of the present invention is a hydrogen chloride gas and silicon produced by mixing chlorosilane gas and hydrogen gas at high temperature. To a seed rod of a silicon single crystal, and a silicon single crystal produced by growing the silicon single crystal while etching the surface of the silicon single crystal with hydrogen chloride gas has an energy on the irradiation surface of 3100 to 3358 mW / cm ² Is irradiated with the laser beam and the emitted spectrum is photoelectrically measured to quantify the ultra-trace element in the silicon single crystal, and the ultra-trace element amount is converted into the amount of the ultra-trace element in the chlorosilane gas.

When the chlorosilane gas in the raw material gas is dichlorosilane, the mixing ratio is 5.0 to 5.5 mol% in the total amount of dichlorosilane and hydrogen gas, and the total flow rate of dichlorosilane and hydrogen gas is 800. ~ 850 liters /
The time and temperature are preferably 1250 to 1280 ° C. When the chlorosilane gas in the raw material gas is trichlorosilane, the mixing ratio is 9.0 to 9.5 mol% in the total amount of trichlorosilane and hydrogen gas, and the total flow rate of trichlorosilane and hydrogen gas is 960 to 990 liters. / Hour, the temperature is preferably 1200 to 1250 ° C. When the chlorosilane gas in the raw material gas is tetrachlorosilane, the mixing ratio is 12.0 to 12.5 mol% in the total amount of tetrachlorosilane and hydrogen gas, and the total flow rate of tetrachlorosilane and hydrogen gas is 1100 to 1150 liters. / Hour, the temperature is preferably 1150 to 1200 ° C.

Chlorosilane is mixed with hydrogen gas and reduced to silicon at high temperature, and at the same time, hydrogen chloride is by-produced. While hydrogen chloride generated as a by-product etches the silicon single crystal rod, silicon chemically vapor-deposits on the silicon single crystal rod to become a silicon single crystal. The condition for obtaining a single crystal is that the amount of chemical vapor deposition is maintained larger than the amount of etching by which the amount of by-produced hydrogen chloride is maximized.

As shown in FIG. 1, the silicon single crystal ingot 1 has
A single crystal rod with a diameter of about 4 mm bent in a U-shape is used by lying down. In the figure, the ratio of the length a to the length b of the holding structure is important from the hydrodynamic viewpoint of the gas flow in order to improve the effects of the etching and the chemical vapor deposition method. The ratio a / b of length to width is 3: 1 to 12: 1.
Is preferred. The cross-sectional shape of the silicon single crystal ingot may be round or square.

When a silicon single crystal obtained by the chemical vapor deposition method under the above conditions is irradiated with a laser beam having an energy on the irradiation surface of 3100 to 3358 mW / cm ² , a spectrum having a good S / N ratio is given. Be done.
Since this silicon single crystal contains crystal defects, only a spectrum having a low S / N ratio can be obtained even when irradiated with a low energy laser beam, and thus it is not possible to separately quantify ultratrace elements. For the determination of ultratrace elements, free excitons were trapped in ultratrace elements by giving energy above the transition energy (band gap) between the valence band and conduction band of silicon in liquid helium (4 ° K). After the bound excitons recombine, they emit light, and the intensity of this emission spectrum is measured. To perform the quantification, calibration with a standard substance whose concentration of the ultratrace element is known in advance is performed. The reason why a silicon single crystal containing a crystal defect does not give a good spectrum even when irradiated with a low energy laser beam is that the above-mentioned bound excitons give energy to local strains associated with crystal defects and transition defects It is thought to be due to going through.

Therefore, when a more intense laser beam was irradiated for the purpose of improving the efficiency of recombination / transition of the bound excitons, the S / N ratio was slightly improved. Further S / N
In order to improve the ratio, a detailed study was conducted on spectroscopic factors, detector response, etc., and the S / N ratio was further improved to give a good spectrum, and it was possible to measure the amount of ultratrace elements. Came to. The laser beam is preferably an argon laser. The excitation laser irradiation output is 600 to 650 mW (optical path length from the laser to the sample surface is 1.3 m) at a wavelength of 5145 Å. The slit width at the entrance and exit of the spectroscope (using 8 aspherical lenses in 8 groups for the condensing system and having 1200 gratings / mm) is 600
~ 700 μm, wavelength feed rate of spectroscope is 0.5 ~ 0.7
Å / second. A photomultiplier tube is used for the detector, and the time constant of the photomultiplier tube is 3 to 4 seconds.

[0016]

EXAMPLES Examples of the present invention will be described below.

Example 1 A seed rod of silicon single crystal was used as the solid phase, and the holding structure (see FIG. 1) had a length to width ratio of 6. A mixed gas of trichlorosilane and hydrogen gas was used as a raw material gas. The mixing ratio of trichlorosilane was 9.0 mol% with respect to the total amount of raw material gas. The flow rate of the raw material gas was set to 960 liters / hour, the temperature was set to 1200 ° C., and a silicon single crystal was produced by the chemical vapor deposition method. The generated silicon single crystal was irradiated with a laser beam under the conditions shown in Table 1, and the emitted spectrum was photoelectrically measured to separately and quantitatively determine the concentration of the ultratrace element. The S / N ratio of the measurement result is shown in Table 1. The measurement results are shown in the chart of FIG.
The concentrations of ultratrace elements are shown in Table 2.

Comparative Example 1 A silicon polycrystalline seed rod was used as a solid phase, and the sample trichlorosilane was heated and reduced with hydrogen gas by a chemical vapor deposition method to generate a silicon polycrystalline. A part of this silicon polycrystal was sampled and a silicon single crystal was obtained by the zone float method. After measuring the resistivity of the silicon single crystal, the band-floating method is further repeated several times in vacuum to remove the donors (phosphorus and arsenic), and the resistivity is measured again to measure the residual acceptors (boron and aluminum). The total concentration was calculated. The total concentration of phosphorus and arsenic was calculated from the difference in resistivity by calculating the difference between the previously measured resistivity and the later measured resistivity. The results are shown in Table 2.

The concentrations shown in Table 2 are ppta (part per trillio
n atomic), and the calculation to convert this into a resistance value is as follows.

Resistance value = 1000 × 93 / {[P + As (ppta)] − [B + Al (ppta)]} Resistance value of the silicon single crystal manufactured in Example 1 = 1000 × 93 / {[104 + 2]-[ 21 + 2]} = 1120 (Ω · cm) Resistance value of the silicon single crystal produced in Comparative Example 1 = 1000 × 93 / {[170] − [38]} = 704 (Ω · cm) Table 2 shows measured resistance values. Is also shown. It can be seen that the resistance value converted from the concentration obtained by the quantification according to Example 1 is closer to the measured resistance value than the resistance value converted from the concentration obtained by the quantification according to Comparative Example 1.

Comparative Example 2 In the same manner as in Example 1, a silicon single crystal was produced by the chemical vapor deposition method. The generated silicon single crystal was irradiated with a laser beam under the conditions shown in Table 1, and the emitted spectrum was photoelectrically measured to separately and quantitatively determine the concentration of the ultratrace element. The S / N ratio of the measurement result is shown in Table 1. The measurement results are shown in the chart of FIG.

[0022]

[Table 1]

[0023]

[Table 2]

As can be seen from Table 2, the lower limit of quantification is 20 ppta in the method of Comparative Example 1, and is the concentration as the total amount of phosphorus and arsenic and the concentration as the total amount of boron and aluminum. The lower limit of quantification of the method of the present invention is 2 p
pta, which can be measured as the concentration of phosphorus, arsenic, boron, and aluminum. This greatly contributes to the production process control of chlorosilane and the production process of silicon single crystal.

[0025]

As described above in detail, in the method for producing a silicon single crystal for semiconductor according to the present invention, the silicon single crystal is directly produced by the chemical vapor deposition method without using the zone-floating-fusing method. Therefore, contamination from the zone floater and blower is eliminated, and a high purity one can be obtained. Further, since the band floating method can be omitted, the complicated and skilled operation is released, and the working time can be shortened.

Further, according to the method of fractionating and quantifying the ultratrace element in the raw material chlorosilanes and the ultratrace element in the produced silicon single crystal of the present invention, the accuracy of ppta can be accurately measured, and the crystal defects can be detected. The ultra-trace element contained in the contained silicon crystal can be similarly measured.

In order to obtain the desired electrical characteristics of the semiconductor, the raw material chlorosilanes include ultratrace elements such as phosphorus, arsenic,
Boron and aluminum are further added as dopants as needed, but according to the method for fractionating and quantifying ultratrace elements of the present invention, the existing amounts of these elements are accurately known. Can be accurately determined.

[Brief description of drawings]

FIG. 1 is a holding structure for a silicon single crystal ingot to which the present invention is applied.

FIG. 2 is a chart of a spectrum obtained by irradiating a silicon single crystal to which the present invention is applied with a laser beam.

[Explanation of symbols]

 1 ... Silicon single crystal rod.

Claims (8)

[Claims] 1. A hydrogen chloride gas produced by mixing at least one kind of chlorosilane gas selected from dichlorosilane, trichlorosilane and tetrachlorosilane and hydrogen gas at high temperature and silicon are supplied to a seed rod of a silicon single crystal. A method for producing a silicon single crystal by a chemical vapor deposition method, which comprises growing the silicon single crystal while etching the surface of the silicon single crystal with hydrogen chloride gas. 2. The chlorosilane gas is dichlorosilane, the mixing ratio thereof is 5.0 to 5.5 mol% in the total amount of dichlorosilane and hydrogen gas, and the total flow rate of dichlorosilane and hydrogen gas is 800 to 850. The method for producing a silicon single crystal by the chemical vapor deposition method according to claim 1, wherein the temperature is 1250 to 1280 ° C. in liter / hour. 3. The chlorosilane gas is trichlorosilane, and the mixing ratio thereof is 9.0 to 9.5 mol% in the total amount of trichlorosilane and hydrogen gas, and the total flow rate of trichlorosilane and hydrogen gas is 960 to 990. The method for producing a silicon single crystal by the chemical vapor deposition method according to claim 1, wherein the temperature is 1200 to 1250 ° C. in liter / hour. 4. The chlorosilane gas is tetrachlorosilane, the mixing ratio thereof is 12.0 to 12.5 mol% in the total amount of tetrachlorosilane and hydrogen gas, and the total flow rate of tetrachlorosilane and hydrogen gas is 1100 to 1150.
The method for producing a silicon single crystal by the chemical vapor deposition method according to claim 1, wherein the temperature is 1150 to 1200 ° C. in liter / hour. 5. A silicon single crystal produced by a chemical vapor deposition method has an irradiation surface energy of 3100-3.
A method for fractionating and quantifying an ultratrace element in a silicon single crystal, which comprises irradiating a laser beam of 358 mW / cm ² and photoelectrically measuring the emitted spectrum to quantify the ultratrace element in the silicon single crystal. 6. The method for fractionating and quantifying ultratrace elements in a silicon single crystal according to claim 5, wherein the laser beam is an Ar laser. 7. Hydrogen chloride gas and silicon produced by mixing chlorosilane gas and hydrogen gas at a high temperature are supplied to a seed rod of a silicon single crystal, and silicon is etched while etching the surface of the silicon single crystal with hydrogen chloride gas. A silicon single crystal produced by growing a single crystal is irradiated with a laser beam having an energy of 3100 to 3358 mW / cm ² on the irradiation surface, and the emitted spectrum is photoelectrically measured to quantify ultratrace elements in the silicon single crystal. Then, the ultratrace element amount in the chlorosilane gas is converted into the amount of the ultratrace element in the chlorosilane gas. 8. The method for fractionating and quantifying ultratrace elements in chlorosilane gas according to claim 7, wherein the laser beam is an Ar laser.