JP4356517B2 - Silicon single crystal pulling apparatus and silicon single crystal manufacturing method - Google Patents

Description

  The present invention relates to a silicon single crystal pulling apparatus and a silicon single crystal manufacturing method for forming a silicon single crystal.

  A single crystal silicon wafer used as a substrate for a semiconductor device or the like is manufactured by slicing a silicon single crystal ingot and performing mirror surface processing or the like. Examples of a method for producing such a silicon single crystal ingot include the Czochralski method (CZ method) and the floating zone method (FZ method). Among them, the CZ method occupies most of the production of a silicon single crystal ingot because it is easy to obtain a large-diameter single crystal ingot and the defect control is relatively easy.

  One of important characteristics required for a single crystal silicon wafer manufactured from such a silicon single crystal ingot is resistivity. This specific resistance changes according to the impurity concentration in the silicon single crystal, and the value is required to be within a certain range according to the application, user's standards, and the like. For this reason, according to the required specific resistance range, a certain amount of impurities (dopant) is added in advance to the silicon melt to carry out pulling growth. However, the specific resistance of the pulled semiconductor single crystal gradually decreases in the growth axis direction because the silicon melt in the crucible decreases and the impurity concentration changes as the growth of the single crystal proceeds.

In order to control such a change in resistivity in the growth axis direction of the silicon single crystal, for example, Patent Document 1 describes an apparatus for adding a dopant impurity during pulling using a conduit. Patent Document 2 describes a method of adding a dopant by inserting a silicon thin rod containing a dopant into a silicon melt in a crucible.
JP 05-032540 A Japanese Patent Laid-Open No. 06-234592

  However, as in the single crystal pulling apparatus described in Patent Document 1 described above, in the method of adding a dopant impurity from a conduit in the course of pulling, since only a predetermined amount is added, the target value of the resistance value is Although there is no change, there is a problem in that the solid dopant floats in the silicon melt until the added dopant is completely melted in the silicon solution, which is in contact with the silicon single crystal being pulled and inhibits single crystallization.

  On the other hand, in the method of adding a dopant with a silicon thin rod containing a dopant as in the single crystal pulling apparatus described in Patent Document 2, a solid dopant before melting can be added without floating in the silicon melt. Therefore, although there is little possibility of inhibiting single crystallization, the amount of dissolved dopant required in mg units varies due to the temperature change of the melt, and as a result, the variation in the hit ratio of the resistance value also increases. There was a problem.

  The present invention has been made in view of the above circumstances, and provides a silicon single crystal pulling apparatus and a silicon single crystal manufacturing method capable of efficiently obtaining semiconductor single crystals having different specific resistance ranges. With the goal.

In order to achieve the above object , according to the silicon single crystal pulling apparatus of the present invention, it has a crucible for containing a silicon melt and a heater for heating the crucible, and the growth axis direction is determined by the Czochralski method. A silicon single crystal pulling apparatus for pulling up a silicon single crystal having a discontinuous resistivity distribution in
An impurity injection device for introducing impurities into the silicon melt during the pulling of the silicon single crystal;
The impurity input device comprises a storage container that stores impurities, and a vertical movement device that inserts and removes the storage container into the crucible,
The storage container includes a cylindrical barrel and a tip portion that extends integrally from the barrel portion, and the tip portion has an open surface that is narrower than the width of the barrel portion. As it forms,
An impurity having a particle size larger than the opening width of the front end portion of the storage container is stored, or an impurity having a particle size smaller than the opening width of the front end portion is stored in the storage container after a silicon plate is installed at the front end portion. It is said that it is supposed to be.
The present invention is a silicon single crystal pulling apparatus having a crucible for containing a silicon melt and a heater for heating the crucible, and pulling up the silicon single crystal by the Czochralski method. There is provided a silicon single crystal pulling apparatus comprising an impurity adding apparatus for introducing impurities into the silicon melt during pulling. Moreover, the said impurity input apparatus should just be comprised from the storage container which accommodates an impurity, and the up-down moving apparatus which inserts / removes this storage container in the said crucible.

  In order to achieve the above object, according to the present invention, a pulling step of pulling a silicon single crystal from a silicon melt, and an impurity adding step of adding impurities to the silicon melt in the course of the pulling step And a silicon single crystal having a specific resistance distribution discontinuous in the growth axis direction is obtained.

  According to the silicon single crystal pulling apparatus of the present invention, solid impurities are drifted in the silicon melt and dissolved in the silicon melt in the quartz crucible while the impurities are dissolved in the storage container. The growth is not hindered, and the amount of dissolved impurities does not vary due to the temperature change of the silicon melt 7. The impurity concentration of the silicon single crystal ingot that has undergone such an impurity injection process changes discontinuously in the growth axis direction.

  In the silicon single crystal ingot pulled up through these steps, the resistivity distribution changes discontinuously in the growth axis direction before and after the impurity addition step. This makes it possible to efficiently obtain a silicon single crystal ingot having specific resistance ranges that differ discontinuously in the growth axis direction according to the application, user specifications, and the like.

  According to the silicon single crystal pulling apparatus of the present invention, it can be obtained.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a partially broken perspective view schematically showing a silicon single crystal pulling apparatus according to the present invention. FIG. 2 is a cross-sectional view of the silicon single crystal pulling apparatus. The silicon single crystal pulling apparatus 10 includes a substantially cylindrical outer shell 11 and accommodates a quartz crucible 12 for melting and storing silicon therein. For example, the outer shell 11 may have a double-wall structure in which a constant gap is formed inside. By flowing the cooling water 13 through the gap, the outer shell 11 is heated when the quartz crucible 12 is heated. To prevent.

  The outer shell 11 is provided with an air supply / exhaust pipe 21, and an inert gas such as argon is introduced into the silicon single crystal pulling apparatus 10 when pulling the silicon single crystal. A pulling drive device 14 is provided on the top of the outer shell 11. The pulling drive device 14 pulls the seed crystal 6 that is a growth nucleus of the silicon single crystal ingot 5 and the silicon single crystal ingot 5 that is grown therefrom while pulling upward.

  A heat insulating cylinder 15 is provided inside the outer shell 11. The heat insulating cylinder 15 may be made of graphite, for example, and serves to reduce the temperature drop during heating of the quartz crucible 12 and to suppress the temperature rise of the outer shell 11.

  A substantially cylindrical side heater 16 is provided inside the heat insulating cylinder 15. The side heater 16 heats the cylindrical body 12 a of the quartz crucible 12. A quartz crucible 12 and a crucible support (graphite crucible) 17 are accommodated inside the side heater 16. The quartz crucible 12 is formed of quartz as a whole and is composed of a substantially cylindrical body 12a having an open surface 12c on the upper side and a mortar-shaped bottom 12b closing the lower side of the body 12a.

  The quartz crucible 12 stores a silicon melt 7 obtained by melting solid silicon. The crucible support 17 is made of, for example, graphite as a whole, and supports the crucible 12 so as to wrap the quartz crucible 12. The crucible support 17 maintains the shape of the quartz crucible 12 softened when silicon is melted and plays a role of supporting the quartz crucible 12.

  A heat insulating cover 31 is formed on the upper surface of the quartz crucible 12 so as to cover the upper surface of the silicon melt 7. The heat insulating cover 31 is formed with an opening through which the silicon single crystal ingot 5 and a storage container 24 of an impurity input device 23 described later are inserted. Such a heat insulating cover 31 suppresses temperature fluctuation of the silicon melt 7.

  A crucible support device 19 is provided below the crucible support 17. The crucible support device 19 supports the crucible support 17 and the quartz crucible 12 from the lower side, and adjusts the position of the quartz crucible 12 corresponding to the liquid surface position of the silicon melt 7 that changes with growth ( (Not shown).

  An impurity injection device 23 is provided on the upper side of the quartz crucible 12. The impurity input device 23 includes a storage container 24 that stores impurities (dopant), and a vertical movement device 25 that inserts and removes the storage container into and from the quartz crucible 12.

  As shown in FIG. 3, the storage container 24 constituting the impurity input device 23 includes a cylindrical trunk portion 24a and a tip portion 24b extending integrally from the trunk portion 24a. The distal end portion 24b is formed to be narrowed so that the distal end portion forms an open surface 24c and becomes narrower than the width W of the body portion.

  Such a storage container 24 stores an impurity (dopant) that is melted into the silicon melt while the silicon single crystal is being pulled. For example, as shown in a of FIG. 3, impurities 26 a having a particle size larger than the opening width S of the tip 24 b of the storage container 24 may be stored in the storage container 24.

  Further, for example, as shown in FIG. 3b, when the impurity 26b having a particle size smaller than the opening width S of the tip 24b is stored in the storage container 24, a silicon plate 27 or the like is installed on the tip 24b. The impurities 26b having a particle size smaller than the opening width S may be stored in the storage container 24.

  The vertical movement device 25 holds the storage container 24 containing such impurities 26 on the quartz crucible 12, lowers the storage container 24 while being pulled up, and immerses the storage container 24 in the silicon melt 7. The vertical movement apparatus 25 is installed so that it may be located outside the outer edge P of the quartz crucible 12 shown in FIG. As a result, the vertical movement device 25 is located at a position avoiding directly above the silicon melt 7 and prevents dust or the like accompanying the vertical movement from falling on the silicon melt 7 and affecting the pulling up.

  Next, with reference to FIGS. 4 and 5, a method for producing a silicon single crystal of the present invention using the silicon single crystal pulling apparatus of the present invention will be described. First, before starting the pulling, after storing impurities (dopants) in the storage container 24 of the impurity input device 23, the vertical movement device 25 is operated so that the tip 24 b of the storage container 24 is above the upper surface of the quartz crucible 12. The storage container 24 is raised to a position (see FIG. 4). Note that the amount of impurities (dopant) accommodated in the storage container 24 may be an amount calculated in advance so as to have a concentration according to the purpose of use, user specifications, and the like.

  The quartz crucible 12 is heated by the side heater 16 to melt the raw material silicon to form the silicon melt 7 and grow the silicon single crystal ingot 5 (pulling process). When the silicon single crystal ingot 5 is pulled up to a predetermined length and the silicon melt 7 in the quartz crucible 12 is reduced to a predetermined amount, the vertical movement device 25 is operated to immerse the storage container 24 in the silicon melt 7. The storage container 24 is lowered (see FIG. 5).

  When the storage container 24 is lowered and immersed in the silicon melt 7, the silicon melt 7 enters the storage container 24 from the open surface 24 c of the storage container 24 shown in FIG. 3, and the impurities stored in the storage container 24. 26 is dissolved (impurity charging step). Then, the dissolved impurities 26 diffuse into the silicon melt 7 in the quartz crucible 12 and increase the impurity concentration in the silicon melt 7 to a predetermined value.

  In this way, by dissolving the impurities 26 in the storage container 24 and diffusing them into the silicon melt 7 in the quartz crucible 12, solid impurities drift in the silicon melt 7 and inhibit the growth of the silicon single crystal ingot. There is no variation in the amount of dissolved impurities due to the temperature change of the silicon melt 7. The silicon single crystal ingot 5 that has undergone such an impurity injection process has its impurity concentration discontinuously changed in the growth axis direction, and the silicon single crystal ingot 5 continues to be pulled up.

  In the silicon single crystal ingot 5 pulled through these steps, the specific resistance distribution changes discontinuously in the growth axis direction before and after the impurity addition step. This makes it possible to efficiently obtain a silicon single crystal ingot having specific resistance ranges that differ discontinuously in the growth axis direction according to the application, user specifications, and the like.

  The present applicant verified the characteristics of a silicon single crystal ingot obtained by using the silicon single crystal pulling apparatus of the present invention as described above. In the verification, with respect to the silicon single crystal pulled using the silicon single crystal pulling apparatus shown in FIGS. 1 and 2, the variation in the hit ratio of the preset specific resistance (target resistance) and the single crystallization rate Examined. Further, as a comparative example, the variation of the target resistance ratio and the single crystallization rate were similarly investigated for the silicon single crystal (two examples) pulled using the conventional silicon single crystal pulling apparatus. These verification results are shown in Table 1.

  According to the results shown in Table 1, in the conventional comparative example, the single crystallization rate decreases when trying to reduce the dispersion of the target resistive median, and conversely when the single crystallization rate is increased, the target resistive median Although the result showed that the variation became large, in the present invention, it was confirmed that the single crystallization rate could be kept good while reducing the variation in the resistance median.

FIG. 1 is a partially broken perspective view schematically showing a silicon single crystal pulling apparatus according to the present invention. FIG. 2 is a sectional view schematically showing the silicon single crystal pulling apparatus of the present invention. FIG. 3 is a cross-sectional view showing a storage container of the impurity input device. FIG. 4 is an explanatory view showing a method for producing a silicon single crystal according to the present invention. FIG. 5 is an explanatory view showing a method for producing a silicon single crystal according to the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Silicon single crystal pulling apparatus 12 Quartz crucible 12a Body part 12b Bottom part 12c Open surface 16 Side heater 23 Impurity throwing apparatus 24 Storage container 25 Vertical motion apparatus

Claims (1)

A silicon single crystal pulling apparatus having a crucible for containing a silicon melt and a heater for heating the crucible, and pulling up a silicon single crystal having a discontinuous resistivity distribution in the growth axis direction by the Czochralski method. And
An impurity injection device for introducing impurities into the silicon melt during the pulling of the silicon single crystal ;
The impurity input device comprises a storage container that stores impurities, and a vertical movement device that inserts and removes the storage container into the crucible,
The storage container includes a cylindrical barrel and a tip portion that extends integrally from the barrel portion, and the tip portion has an open surface that is narrower than the width of the barrel portion. As it forms,
An impurity having a particle size larger than the opening width of the front end portion of the storage container is stored, or an impurity having a particle size smaller than the opening width of the front end portion is stored in the storage container after a silicon plate is installed at the front end portion. A silicon single crystal pulling apparatus characterized by that.

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