KR100470858B1 - Polycrystalline Silicon Rod and Process for Preparing the Same - Google Patents

Abstract

In the present invention, the peak of the X-ray diffraction pattern showing the crystal orientation 111 is 0.3 degrees or less, the internal stress strain in the radial direction is less than 5.0 × 10 ^-5 cm ^-1 and the internal iron concentration is 0.5 ppba or less A polycrystalline silicon rod is characterized by.

This high crystal, high purity, and low internal stress strain polycrystalline silicon rod heats the silicon core in a gas atmosphere consisting of trichlorosilane and hydrogen, and precipitates silicon on the silicon core to produce a polycrystalline silicon rod, and then the polycrystalline silicon It is produced by reducing the inherent stress deformation by heat treatment without contacting the rod to the outside air.

Description

Polycrystalline Silicon Rod and Process for Manufacturing the Same

The present invention relates to a polycrystalline silicon rod having a low internal stress deformation and having uniform high crystallinity and a method of manufacturing the same. More specifically, when the silicon single crystal used in the manufacture of devices is manufactured by recharging or the like, even if directly supplied to the melting furnace, residual stress deformation is reduced to the extent that the problem caused by cracking can be prevented, and stable melting characteristics are achieved. It relates to a high purity polycrystalline silicon rod having a and a method of manufacturing the same.

In general, polycrystalline silicon rods are manufactured by chemical vapor deposition (hereinafter, simply CVD method). That is, the CVD method generally comes into contact with a core material maintained at high temperature in a gas atmosphere in which a mixture of silane gases such as monosilane, dichlorosilane, trichlorosilane, or two or more kinds of mixed gases and hydrogen is diluted with an inert gas, if necessary. It is carried out by depositing silicon on the surface of the core material. Among such precipitation methods of polycrystalline silicon by the CVD method, there is a method of manufacturing a polycrystalline silicon rod by thickening a rod using silicon as a core material. This method is also known as the Siemens method and is widely used.

On the other hand, attempts have been made to melt the polycrystalline silicon rod manufactured by the Siemens method as it is and to single crystallize by recharging.

Japanese Patent Laid-Open No. 7-277874 discloses a technique for producing single crystal silicon by supplying the silicon rod as it is as a rod for recharging.

This publication discloses the necessity of reducing the residual stress of a polycrystalline silicon rod in order to prevent the fall of the polycrystalline silicon rod of a raw material during the production of single crystal, and as a concrete means for this, polycrystalline silicon using monosilane as a raw material. A method of manufacturing a rod is disclosed. In addition, since polycrystalline silicon rods obtained from raw materials other than monosilane have a large residual stress, it is also disclosed to remove such residual stress by performing heat treatment such as annealing before melting.

However, polycrystalline silicon rods produced industrially using monosilane as a raw material generally have low crystallinity of the resulting polycrystalline silicon rods. That is, the polycrystalline silicon rod manufactured using monosilane as a raw material has a half width of 0.4 ° to 0.5 ° of a peak near 2θ = 28.5 ° of the X-ray diffraction pattern targeted to copper (hereinafter also referred to as (111) peak). It is enough.

Therefore, the polycrystalline silicon rod manufactured using such monosilane as a raw material has a low crystallinity, and therefore, when the surface is etched in order to obtain high purity single crystal silicon, in particular, to avoid the incorporation of heavy metals, The amorphous portion remains as a hole, causing problems such as the remaining of the etching solution.

This is also estimated from the fact that fine powder formed by homogeneous reaction enters the polycrystalline silicon rod deposited by monosilane in JP-A-8-169797.

In addition, Japanese Patent Laid-Open No. 8-67510 discloses that the surface area of the polycrystalline polysilicon having low crystallinity is increased by etching.

On the other hand, the polycrystalline silicon rod manufactured using trichlorosilane as a raw material has high crystallinity and there is no homogeneous reaction, so no fine powder enters.

Therefore, the polycrystalline silicon rod manufactured using trichlorosilane as a raw material does not deteriorate in quality due to etching because the surface after etching is also slippery. In addition, since trichlorosilane has a very low raw material cost compared to monosilane, it has been desired to use polycrystalline silicon rods based on trichlorosilane for recharging.

By the way, the polycrystalline silicon rod manufactured using trichlorosilane as a raw material has a large residual stress in the rod, as described in Japanese Patent Application Laid-Open No. 7-277874. Therefore, it is applicable to FZ or a rod for recharging. Was considered inappropriate.

When the residual stress of the polycrystalline silicon rod is to be removed and heat treatment such as annealing is performed before melting the polycrystalline silicon rod, its purity is markedly degraded due to contamination, so that the polycrystalline silicon rod cannot be used for the preparation of the single crystal.

That is, since the heat treatment before melting of the polycrystalline silicon rod is carried out after removing it from the precipitation reaction vessel, the surface is contaminated with iron of about 1 × 10 ¹⁵ atoms / cm ² by contact with impurities in the air during the transfer. . This surface contamination diffuses into the rod during heat treatment, resulting in contamination of about 7 ppba.

In addition, since the heat treatment is performed at a temperature of 1100 ° C. or higher, internal contamination by dopant impurities or heavy metal impurities emitted from the heater or the container is also concerned.

In order to use the heat-treated polycrystalline silicon rod in the manufacturing process of single crystal silicon, even though the surface is etched in the clean room before melting to remove the contamination of the outer surface, the rod does not return to the clean state twice. Adversely affects the purity of the product.

As a method of preventing contamination of such polycrystalline silicon rods, a method of protecting the rods with a quartz glass tube can be considered. Since quartz glass softens at 1000 ° C or higher, this method is not an effective method.

<Start of invention>

Accordingly, an object of the present invention is to provide a high-purity polycrystalline silicon rod with high crystallinity, very low impurity content representing iron, and very low residual stress.

Another object of the present invention is to provide a method of industrially advantageously and efficiently producing the polycrystalline silicon rod of the present invention.

Still other objects and advantages of the present invention will become apparent from the following description.

According to the present invention, the above object and advantage of the present invention are as follows. First, the half width of the peak of the X-ray diffraction pattern showing the crystal orientation 111 is 0.3 ° or less, and the internal stress strain in the radial direction is 5.0 × 10 ⁻⁵ cm. A polycrystalline silicon rod is characterized by less than ^-1 and an internal iron concentration of 0.5 ppba or less.

In addition, according to the present invention, the above object and advantage of the present invention are secondly to obtain the polycrystalline silicon rod, that is, by heating a silicon core in a gas atmosphere composed of trichlorosilane and hydrogen, and depositing silicon on the silicon core A polycrystalline silicon rod is produced, and then heat treated without contacting this polycrystalline silicon rod to achieve an intrinsic stress strain, thereby achieving the polycrystalline silicon rod manufacturing method.

BRIEF DESCRIPTION OF THE DRAWINGS It is a schematic diagram which shows the stress deformation of the r, (theta), and z direction which exists in the inside of the precipitated polycrystalline silicon rod.

Fig. 2 is a dotted line diagram showing the stress strain distribution in the r direction inside the rod.

3 shows a temperature distribution curve drawn as a calculated value inside the rod during energizing heating and after stopping energization.

In FIG. 2, (1) shows the internal stress deformation, (3) shows the temperature distribution curve in the rod when surface temperature is 1150 degreeC, and (3) shows the elapse of 1 minute after momentarily stopping energization. (4) shows the temperature distribution curve in a rod, and (4) shows the temperature distribution curve in a rod when 5 minutes has passed and power supply is momentarily stopped, respectively.

The polycrystalline silicon rod of the present invention has a half width of 0.3 ° of the peak (peak having a 2θ of about 28.5 °) showing the pattern crystal orientation 111 of X-ray diffraction (hereinafter, also simply referred to as X-ray diffraction) targeting copper. Ihara has high crystallinity.

The polycrystalline silicon rod whose half width of the specific peak representing the crystal orientation 111 exceeds 0.3 ° is likely to form holes in the surface by etching or the like due to the presence of an amorphous portion, This is not an object of the present invention because it causes a decrease in purity of the polycrystalline silicon rod.

The above-mentioned polycrystalline silicon rod manufactured from monosilane as a raw material includes silicon fine powder formed by a homogeneous reaction therein, so that the half peak width of a specific peak having low crystallinity and usually showing crystallinity is about 0.4 ° to 0.5 °. to be.

Therefore, in the present invention, the half value width of the specific peak indicating the crystallinity of the polycrystalline silicon is preferably smaller within the above range, and the half value width of the X-ray diffraction pattern specific peak is 0.2 ° or less, in particular 0.17 ° or less, furthermore It is preferable that it is 0.16 degrees or less.

The polycrystalline silicon rod of the present invention has the above high crystallinity and satisfies that the internal stress strain in the radial direction is less than 5.0 × 10 ⁻⁵ cm ⁻¹ . In other words, in order to solve the problem of rod cracking when monocrystallization using a polycrystalline silicon rod directly, it is important that the value of the difference between the maximum stress deformation and the minimum stress deformation per 1 cm of the radial direction is small.

In addition, the internal stress strain of the polycrystalline silicon rod precipitated by the Siemens method using trichlorosilane as a raw material is about 1x10 <^-4> cm <^-1> , and some cracks generate | occur | produced before taking out from a precipitation reaction container. If a rod having an internal stress strain of about 1 × 10 ⁻⁴ cm ⁻¹ or more is cracked and stress strain is released, the internal stress strain of the limit for keeping the rod free of cracks is about 1 × 10 ⁻⁴ cm ^{− 1} is judged. However, during the single crystallization of the polycrystalline silicon rod, thermal shock is applied to the rod in order to partially melt the rod. Although the stress strain by the above-mentioned thermal shock changes with conditions, it is estimated that it is about 5x10 <^-5> cm <^{-1> in} r direction. It is thought that a crack occurs when the synthetic strain of the stress strain which the rod has from the beginning and the stress strain applied by thermal shock becomes 1x10 <^-4> cm <^-1> or more mentioned above. Therefore, the internal stress strain of the polycrystalline silicon rod in the present invention is less than 5 × 10 ^-5 cm ^-1 , preferably 3 × 10 ^-5 cm ^-1 or less, more preferably 2 × 10 ^-5 cm ^-1 or less to be.

In the present invention, the internal stress strain of the polycrystalline silicon rod is measured as follows.

As for the internal stress deformation of the polycrystalline silicon rod, as shown in Fig. 1, the r direction in the circumferential coordinate axis (direction from the center to the outside in the cross section perpendicular to the longitudinal direction of the rod) and the θ direction (perpendicular to the longitudinal direction of the rod) It is decomposed into three components in the circumferential direction perpendicular to the r direction in the cross section and in the z direction (the longitudinal direction of the rod).

In order to measure the internal stress deformation in the r direction and the θ direction, the rod is cut at a position perpendicular to the longitudinal direction at the measurement position, and then cut at another position to process a short rod. It is preferable that the length of this rod is 300 mm or more and 400 mm or less. If the length of the short bar is 300 mm or less, the amount of deformation due to cutting increases, making it difficult to accurately measure stress deformation. If the short bar is too long, the operation becomes difficult. After the rod is made into a short rod, the measuring surface is processed into a smooth surface, and then roughened and cleaned with diamond or paper of about # 200. After drying this cleaning surface, a strain gauge is affixed in the direction which can measure the stress deformation of r direction and (theta) direction. In order to eliminate the influence of stress strain variation due to the orientation of the rod, the strain gage is attached as much as possible in a straight line from the center of the rod cross section outward. In order to reduce the error by measurement, the interval between applying the strain gauge is preferably 10 mm or less, more preferably 7 mm or less. In addition, by attaching a strain gauge in various directions radially from the center, it is possible to measure in-plane stress strain distribution in more detail. Subsequently, the stress strain is released by cutting the position where the strain gauge is applied into a rectangular parallelepiped about 7 x 7 x 5 mmt. In order to measure the stress deformation in the z direction, the short rod-shaped rod may be further cut in the longitudinal direction including the central axis, and the same operation as the stress deformation measurement in the r direction and the θ direction may be performed. However, since the stress strain is reduced by longitudinal cutting when working into a short rod, the obtained value is slightly smaller than it actually is.

The stress strain measured by the strain gauge is represented by the value of ㅿ L / (L + ㅿ L) when L is the initial length of the material strained and L + L is the length after the stress strain is removed. Therefore, there is no unit in the value of stress deformation. The sign of stress deformation is negative in tension and positive in compression.

The value of the stress deformation in the r direction obtained by the above method is distributed as shown in FIG. 2. The difference between the maximum value and the minimum value in these measured values is defined as internal stress deformation of the rod. In addition, the value obtained by dividing the internal stress deformation in the r direction by the radius of the rod (unit: cm) is the internal stress deformation that exists per unit volume of the rod, that is, the internal stress strain (unit: cm ⁻¹ ).

The internal stress strain in the present invention shall be calculated from the value of the stress strain in the r direction. The internal stress strains in the r, θ, and z directions are all correlated, for example, a rod having a large internal stress strain in the r direction is also largely proportional to the internal stress strains in the θ and z directions. Also, among these, the value is most stably obtained in the r direction. For this reason, the value of the stress deformation in the r direction is most suitable for the calculation of the internal stress strain. Specifically, the strain gauge is used to smooth the value of the stress strain in the r direction measured from at least one direction, preferably two or more directions, from the center of the rod to the outer periphery using a three-point smoothing method. The difference between the maximum and minimum values is obtained from the value, and the difference is divided by the average radius of the rod from the center to the outer periphery (in cm).

The polycrystalline silicon rod of the present invention is also characterized in that the iron concentration therein is 0.5 ppba or less. In other words, when the iron concentration in the polycrystalline silicon rod exceeds 0.5 ppba, it can no longer be used as a raw material for monocrystalline silicon production.

As described above, the method of removing the internal stress strain by annealing the polycrystalline silicon rod in which the stress strain is present can be considered as a general method. When the polycrystalline silicon rod is taken out from the precipitation reaction vessel to anneal the polycrystalline silicon rod, the surface immediately becomes × 10 ¹⁵ is the degree of iron contamination atoms / cm ^2. This surface contamination diffuses into the rod during annealing and becomes about 7 ppba. In contrast, the polycrystalline silicon rod of the present invention has a very high purity in which the iron concentration is 0.5 ppba or less, in particular 0.1 ppba or less, by employing a special heat treatment method described later.

In the polycrystalline silicon rod of the present invention, the content of other impurities other than iron, such as Cu, Ni, Cr, and the like, is preferably smaller, and the metal concentration containing iron is preferably 1 ppba or less, in particular 0.5 ppba or less. Do.

The diameter of the polycrystalline silicon rod of the present invention is not particularly limited and is appropriately determined by the length of the rod, the size of the single crystal silicon manufacturing apparatus, and the like, and the effect of the present invention is remarkably 80 to 200 mm, especially 120 to 200 mm. .

According to the present invention, a polycrystalline silicon rod having such high crystal, high purity and low internal stress strain in the present invention is suitably manufactured by the following method.

That is, the polycrystalline silicon rod of the present invention heats the silicon core material in a gas atmosphere composed of trichlorosilane and hydrogen, and deposits silicon on the silicon core material to produce a polycrystalline silicon rod, and then the polycrystalline silicon rod is not brought into contact with outside air. It can be produced by heat treatment without reducing stress strain.

In particular, in the above method, the polycrystalline silicon rod is contacted with outside air and the stress deformation inherent therein is reduced, followed by the precipitation reaction of silicon followed by energizing the polycrystalline silicon rod in the presence of hydrogen or an inert gas. By heating at least a part of the surface higher than the temperature at the time of the silicon precipitation reaction and exhibiting a temperature of 1030 ° C. or higher, and then stopping the energization and employing a method of cooling, the effect of removing the internal stress strain is high, thereby increasing the amount of impurities other than iron. It becomes possible to be remarkably reduced and is preferable.

In the above method, in a method of manufacturing a polycrystalline silicon rod by heating a silicon core material under a gas atmosphere composed of trichlorosilane and hydrogen and depositing silicon on the silicon core material, known reaction apparatuses, reaction conditions, etc. may be employed without particular limitation. have. In general, a bell-jar is used as a reaction apparatus, and a silicon core material is disposed in the bell-za so as to be energized, and a mixed gas consisting of trichlorosilane and hydrogen is supplied into the bell-za. do. The mixing ratio of such trichlorosilane and hydrogen is usually 5 to 10, preferably 7 to 9, in molar ratio. Moreover, you may dilute and supply the said mixed gas with inert gas, such as Ar and He, as needed.

Precipitation of silicon is made by sending a direct current or alternating current to a silicon core in the gas atmosphere which consists of said chlorosilane and hydrogen, and heating this silicon rod to 900 degreeC-1000 degreeC.

However, polycrystalline silicon rods made from trichlorosilane as a raw material have a large internal stress strain as described above.

It is a feature of the present invention to heat-treat the polycrystalline polysilicon rods produced in a reaction vessel without contacting outside air to remove the internal stress deformation. Since the surface of the rod taken out of the precipitation reactor is very active, when it is heated after contacting with the outside air, a large amount of metal impurities including iron in the outside air adhere to the polycrystalline polysilicon rod, which is heat-treated into the rod. The quality of the polycrystalline polysilicon rod, which is obtained by diffusion and contamination, is significantly reduced.

In the method of the present invention, the means for heating the polycrystalline polysilicon rod without bringing it into contact with the outside air is not particularly limited, but the most suitable method is as described above, following the reaction of silicon, followed by hydrogen or an inert gas such as Ar, He or the like. Accordingly, a current is sent to the polycrystalline silicon rod in the presence of trichlorosilane to heat the surface temperature to 1030 ° C or higher, preferably 1100 ° C or higher, more preferably 1150 ° C or higher, and stop the heating current after a certain time. to be. According to this method, since it is internal heating, the contamination of the rod by the impurities which generate | occur | produce in a heater like the case of using a heater as external heating can also be prevented effectively.

In addition, it is preferable that the heat treatment temperature is generally performed at, for example, a surface temperature of 1300 ° C. or lower so that the inside of the polycrystalline silicon maintains a temperature below the melting point in order to prevent danger.

The inventors have found that the surface temperature of the polycrystalline silicon rod is higher than the temperature at the time of the silicon precipitation reaction, and the internal stress strain of the rod decreases only when the temperature is 1030 ° C or higher, particularly 1100 ° C or higher. Therefore, when the surface temperature of the rod before stopping energization was less than 1000 ° C., the phenomenon of lowering the internal stress strain did not appear, and the internal stress strain of any rod was the same.

The electric current used for the said energization may be either direct current or alternating current, and the power supply at the time of load precipitation can be used as it is.

In order to raise the surface temperature of a polycrystalline silicon rod, in addition to the method of raising the electric current value for heating, it is achieved by changing the atmosphere which heats a rod to the state with low thermal conductivity. In this case, since the temperature difference of a rod center part and an outer peripheral part becomes smaller, it is especially preferable. For example, even if the current value is the same, the hydrogen gas atmosphere can maintain the surface temperature higher than the silane gas atmosphere, and the difference in thermal expansion due to the temperature difference between the center portion and the outer peripheral portion can be made small. In addition, although the surface temperature can be made higher by setting another gas atmosphere, the method of suppressing the heat radiation from the rod surface to the limit by reducing pressure to the limit and reducing the temperature difference of the center part and the outer peripheral part can also be employ | adopted.

In addition, the meaning of `` to conduct electricity following the silicon reaction '' means that if the current is to be sent to the polycrystalline silicon rod again, if the temperature of the polycrystalline silicon rod is too low, the resistance is too high and the intended energization becomes difficult. It's there. Specifically, it may be energized after the temperature of the rod is lowered within the range of the energization possible even if not immediately after being continuously energized immediately after production.

Although it does not specifically limit as a surface temperature measuring method of a rod, In order to measure the temperature of the high temperature surface of 1000 degreeC or more, a radiation thermometer can be used suitably.

In the method for producing a silicon rod of the present invention, the stopping of the energization performed after heating is preferably performed by lowering the energized current as rapidly as possible to effectively perform the heat treatment. Then, a few minutes after the interruption of the current becomes a substantial heat treatment time.

As a preferable aspect which achieves the said heat processing, the method of sending out an electric current to a polycrystalline silicon rod, heating it to 1030 degreeC or more, and then blocking and cooling it at once, without slowing down an electric current, is mentioned. For example, in a rod having a diameter of 120 mm, it is preferable to set it as half or less of the current value before the stop operation within one minute after starting the current drop. As the diameter increases, the heat amount of the rod also increases, and heat dissipation on the surface of the rod takes time, so the current drop speed is allowed to be set slightly slower.

In the present invention, the heat treatment of the polycrystalline silicon rod is preferably performed for as long as possible in order to sufficiently remove stress deformation. For this reason, a gas having a small thermal conductivity is suitably used as the atmosphere gas.

In general, in order to stop the energization so as not to leave stress deformation in the polycrystalline silicon rod, it is generally considered that it is desirable to reduce the current and decrease the cooling rate very slowly. On the other hand, as in the method of manufacturing the polycrystalline silicon rod of the present invention, it is thought that the sudden interruption of the heating current deviates from the common sense for the purpose of not leaving stress deformation. However, this phenomenon can be explained as follows.

Polycrystalline silicon has a property that the higher the temperature, the smaller the electrical resistance value. In the case of heating and precipitation of polycrystalline silicon by energization, the surface of the rod is cooled by heat dissipation and the temperature is lowered, thereby increasing the electrical resistance value. As a result, the current tends to pass through the center portion, increasing the center temperature and lowering the temperature of the rod surface. As a result, the center of the rod is kept at a considerably higher temperature than the outer circumference.

When the current is lowered slowly, this temperature difference is almost maintained and cooled. With cooling, the silicon cannot gradually deform. It is thought that the stress deformation remains due to the difference in thermal expansion because the amount of heat shrinkage between the inside and the outside is different at the stage where the current is finally lowered to finally bring the current back to zero and the temperature of the inside and the outer periphery are the same.

On the other hand, when the surface temperature of the rod is higher than the temperature at the time of the silicon precipitation reaction and the current is suddenly stopped when the rod temperature is higher than 1030 ° C., it is considered that the temperature difference between the inner and outer circumferences decreases while the inside of the rod is still high temperature, and the temperature is almost the same. . This was also confirmed from the measurement that the surface temperature temporarily increased when the current was stopped. If the temperature of the rod is still high enough to deform the silicon at the time when the current stops and the temperature difference between the inner and outer circumferences disappears, the load deforms and the residual stress deformation is reduced, although it is a short time while the temperature is lowered. I think.

As described above, it is considered that stress deformation of the rod occurs due to uneven temperature distribution in the rod due to current heating. However, the temperature distribution in the rod cannot be measured directly. In order to prove the above, the present inventors calculated the temperature distribution in the rod at the time of energization heating and after stopping electricity supply by calculation of the abnormal heat conduction by the difference method. As an example, FIG. 3 shows the transition of the temperature distribution inside the rod when energizing heating and momentarily stopping the energization until the surface temperature of the rod reaches 1150 ° C. Curve 2 in the figure is a temperature distribution curve inside the rod when the surface temperature is 1150 ° C. The temperature at the rod center is estimated to be about 100 ° C. higher than the outer circumference. In addition, curves 3 and 4 are curves which estimate the temperature inside the rod after 1 minute and 5 minutes after the energization is momentarily stopped, respectively. It is calculated that after 1 minute of stopping the energization, the surface temperature of the rod temporarily rises due to cracking, and after 5 minutes, the temperature of the outer peripheral part and the center part becomes almost uniform. Moreover, the temperature at that time is 1100 degreeC or more. This temperature is the temperature at which the polycrystalline silicon is deformed. That is, although it is a short time (usually 7 to 8 minutes after stopping), since the temperature which a rod deform | transforms lasts, it is thought that the temperature of an outer periphery part and a center part is the same, and stress deformation is also reduced.

The polycrystalline silicon rod of the present invention has high crystallinity, high purity, and very small internal stress deformation. Therefore, when it is used as it is as a raw material for single crystal pulling by FZ, recharging or the like, stable operation is ensured and the quality of the obtained single crystal can be maintained high.

Moreover, the manufacturing method of the polycrystalline silicon rod of this invention is very efficient, and it is possible to obtain the polycrystalline silicon rod economically.

In order to explain the present invention in more detail, the following examples and comparative examples will be described, but the present invention is not limited to these examples.

<Example 1>

After the polycrystalline silicon having a diameter of 120 mm was precipitated by the Siemens method, the deposition reaction vessel was replaced with a hydrogen atmosphere, and the current value was controlled to maintain a surface temperature of 1000 mm height at the bottom of the rod at 1100 ° C. for 1 hour. After that, the energization was stopped momentarily. The surface temperature measurement of the rod used the radiation thermometer. After cooling, the rod was removed from the precipitation reactor, and the stress deformation in the r direction at a height of 1000 mm at the bottom of the rod was measured using a strain gauge. In addition, the rod was cut out by a core drill having an internal diameter of ø20 mm, and the results of the measurement of the concentration of iron and other metals in the interior by ICP-MS and neutron radiation analysis were shown in Table 1. In addition, the value of the internal stress strain was also shown in Table 1. Moreover, the half value width of the peak whose 2 (theta) which shows the crystal orientation 111 of the X-ray-diffraction pattern of this rod is about 28.5 degrees was also shown in Table 1.

When 1000 rods were manufactured and melt-heated at the rod end by the above method, cracks were found only for one of the 1000 rods.

<Examples 2 and 3>

Rods were prepared in the same manner as in Example 1 except that the rods had diameters of 100 mm and 140 mm. Table 1 shows the results of measuring the concentration of iron and other metals in the same manner as in Example 1 by ICP-MS. Moreover, the value of the internal stress strain calculated | required by measuring the stress deformation of the r direction was shown in Table 1 together.

When 1000 polycrystalline silicon rods were manufactured and melt-heated at the rod end by the above method, cracks were found in the rods at a rate of 0 out of 1000 in Example 2 and 1 out of 1000 in Example 3.

Diameter (mm) Surface temperature (℃) at the time of stop of electricity supply Internal strain of the rod (cm ^-1 ) (111) half the width of the peak Impurity metal (ppba) Fe Ni Cr Cu Example 1 120 1100 1.5 × 10 ^-5 0.16 0.021 0.014 0.004 <0.2 Example 2 100 1100 1.6 × 10 ^-5 0.16 <0.5 <0.3 <0.3 <0.5 Example 3 140 1100 1.6 × 10 ^-5 0.16 <0.5 <0.3 <0.3 <0.5

<Example 4, Comparative Examples 1 and 2>

The rod was manufactured similarly to Example 1 except having maintained the surface temperature of 1000 mm height at 1050 degreeC, 900 degreeC, and 500 degreeC for 1 hour at the bottom of a rod, respectively. Table 2 shows the results of measuring the concentration of iron and other metals in ICP-MS as in Example 1 with respect to the rod. Moreover, the value of the internal stress strain calculated | required by measuring the stress deformation of the r direction was shown in Table 2 together.

In Comparative Examples 1 and 2, when the surface temperature of the rod was lowered, the temperature was lowered to 3 ° C./min or lower so as to cool slowly.

When 1000 polycrystalline silicon rods were produced by the method of Example 4 and melt-heated at the rod ends, cracks were found in the rods at a ratio of 5 out of 1000.

Thirty rods were manufactured by the method of Comparative Example 2 and melt heating of the rod ends revealed cracking for 19 rods.

Comparative Example 3

At the bottom of the rod, a 1000 mm high surface temperature was maintained at 900 ° C. for 1 hour. After that, the energization was stopped momentarily. After cooling, the rod was taken out of the precipitation reaction vessel, which was heated at 1200 ° C. for 3 hours in an infrared heating furnace and cooled again. The stress deformation in the r direction at the height of 1000 mm at the bottom of this rod was measured. In addition, the rod was cut out with a core drill having an internal diameter of ø20 mm, and the iron concentration therein was measured by ICP-MS. These measurement results are shown in Table 2.

Diameter (mm) Surface temperature (℃) at the time of stop of electricity supply Internal strain of the rod (cm ^-1 ) (111) half the width of the peak Impurity metal (ppba) Fe Ni Cr Cu Example 4 120 1050 2.5 × 10 ^-5 0.16 <0.5 <0.3 <0.3 <0.5 Comparative Example 1 120 900 8.0 × 10 ^-5 0.16 <0.5 <0.3 <0.3 <0.5 Comparative Example 2 120 500 8.0 × 10 ^-5 0.16 <0.5 <0.3 <0.3 <0.5 Comparative Example 3 120 900 → Annealing 1.5 × 10 ^-5 0.16 27 1.4 4.8 <0.5

Claims (2)

The half width of the peak of the X-ray diffraction pattern showing the crystal orientation 111 is 0.3 ° or less, the internal stress strain in the radial direction is less than 5.0 × 10 ⁻⁵ cm ⁻¹ and the iron concentration is 0.5 ppba or less. Polycrystalline silicon rod. The polycrystalline silicon is produced by heating a silicon core under a gas atmosphere composed of trichlorosilane and hydrogen, depositing silicon on the silicon core to produce a polycrystalline silicon rod, and then energizing the polycrystalline silicon rod in the presence of hydrogen or an inert gas. The method of claim 1, wherein the silicon rod is heated until at least a part of the surface of the rod exhibits a temperature of 1030 DEG C or higher, and then the current is stopped and cooled to heat the silicon rod without contacting the outside air to reduce stress deformation. Method for producing a polycrystalline silicon rod.