KR101023318B1 - Method for melting solid raw material for single crystal growth - Google Patents

Abstract

The present invention discloses a melting method of a solid raw material for single crystal growth. The melting method of the solid raw material for single crystal growth according to the present invention comprises a quartz crucible containing a solid raw material, and a solid contained in the quartz crucible in a single crystal manufacturing apparatus using a Czochralski method comprising a heater installed around the quartz crucible sidewall. A method of melting a raw material, the method comprising: (a) filling a solid raw material into the quartz crucible; (b) melting the solid raw material by heating the quartz crucible with the quartz crucible positioned so that the bottom position of the quartz crucible corresponds to the lower part of the heater; And (c) heating the quartz crucible with the quartz crucible positioned so that the melt surface position corresponds to the upper portion of the heater when the solid raw material accommodated in the quartz crucible is melted. It is characterized in that it proceeds for a relatively longer time than the step.

Czochralski (CZ) method, melting process, melt, quartz crucible, heater

Description

Method for melting solid raw material for single crystal growth

The present invention relates to a single crystal growth technology, and more particularly, to a melting method of a solid raw material for single crystal growth, which can efficiently melt a solid raw material used to grow a single crystal when preparing a single crystal using the Czochralski method. .

In general, single crystals used as materials for producing electronic components such as semiconductor devices are manufactured by the Czochralski (hereinafter referred to as CZ) method. In the CZ method, a solid raw material (e.g., polysilicon) filled in a quartz crucible is heated and melted by a heater, followed by dipping a seed into a melt and slowly pulling it upward to grow a single crystal through a solid-liquid interface. It is a way.

The CZ method is largely a melting process for melting solid raw materials, a necking process for growing thin and long single crystals at the beginning of single crystal growth to remove dislocations generated during melt dipping of seeds, and a diameter of the single crystal to a target diameter. An expanding shouldering process, a body growth process for growing a single crystal to be manufactured into a wafer to a certain length, and a tailing process for separating the single crystal from the melt while gradually decreasing the diameter of the single crystal.

On the other hand, in the single crystal grown by the CZ method, the part to be commercialized into the wafer is the body grown in the body growth process. Therefore, in the past, efforts have been made to improve productivity by increasing the crystal quality of the body portion and increasing the pulling speed of the body portion. However, the quality of the wafer is also affected by processes other than the body growth process. In particular, it is known that the melting process of the solid raw material affects the quality of the single crystal grown early in the body process. For example, if the bubbles generated in the melt are not completely removed in the melting process, bubbles are introduced into the single crystal to form an air pocket, which causes a problem that the single crystal grown at the beginning of the body process cannot be commercialized. . In addition, if the position of the quartz crucible relative to the heater is not properly controlled during the progress of the melting process, the solid raw material may suddenly sink and damage the quartz crucible. Therefore, during the melting process, it is also very important to gradually melt the solid material on the top of the quartz crucible to prevent sudden depression of the solid material.

In addition, in recent years, as the large diameter single crystal of 300 mm or more is produced, the capacity of the quartz crucible is gradually increasing. Accordingly, the time required for the melting step of the solid raw material is also gradually increasing. However, if the melting process time is long, the durability of the quartz crucible is weakened, and the yield decreases due to contamination due to crystallization and peeling of the quartz. In order to solve this problem, a method of increasing the power of the heater to shorten the time of the melting process can be considered.However, as the power of the heater increases, the amount of heat transferred to the quartz crucible per unit time increases, which is why There is bound to be a limit.

The present invention has been made to solve the above problems, the object of the present invention is to provide a melting method of the solid raw material for single crystal growth that can shorten the melting process time of the solid raw material and improve the stability of the melting process. .

Another object of the present invention is to provide a method for melting a solid raw material for growing single crystals, which can improve the yield of single crystals by suppressing a factor that adversely affects the quality of the single crystal during the melting process of the solid raw material.

Melting method of a solid raw material for single crystal growth according to the present invention for achieving the above technical problem is a single crystal manufacturing apparatus using a Czochralski method comprising a quartz crucible containing a solid raw material and a heater provided around the quartz crucible sidewall A method of melting a solid raw material contained in the quartz crucible, the method comprising: (a) filling a solid raw material into the quartz crucible; (b) melting the solid raw material by heating the quartz crucible with the quartz crucible positioned so that the bottom position of the quartz crucible corresponds to the lower part of the heater; And (c) heating the quartz crucible with the quartz crucible positioned so that the melt surface position corresponds to the upper portion of the heater when the solid raw material accommodated in the quartz crucible is melted. It is characterized in that it proceeds for a relatively longer time than the step.

Preferably, in the step (b), the position of the quartz crucible is adjusted so that the bottom position of the quartz crucible is between 0 and 1 / 4L based on the length L of the heater.

Preferably, in step (c), the position of the melt surface is adjusted to the position of the quartz crucible so as to be between 3 / 4L and 1L based on the length L of the heater.

Preferably, step (b) is carried out for a time of 85% to 95% based on the total melting process time.

Preferably, step (c) is carried out for a time of 5% to 15% based on the total melting process time.

According to one aspect of the invention, it is possible to shorten the melting process time by efficiently using the amount of heat supplied from the heater.

According to another aspect of the present invention, since it can be gradually melted from the solid raw material on the top of the quartz crucible can improve the stability of the melting process.

According to another aspect of the present invention, the yield of the single crystal can be improved by effectively removing bubbles or the like that adversely affect the quality of the single crystal.

According to another aspect of the present invention, it is possible to shorten the melting process time to prevent deformation of the quartz crucible, to suppress the generation of crystalline precipitates due to the reaction of the quartz and the melt to deteriorate the single crystal quality resulting from the separation of the crystalline precipitates Can be prevented.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. Prior to this, words used in this specification and claims are not to be construed as limiting in their usual or dictionary sense, but rather to properly define the concept of terms in order to best describe the inventor's own invention in the best way possible. It should be interpreted as meaning and concept corresponding to the technical idea of the present invention based on the principle that it can. Therefore, the embodiments described in the specification and the drawings shown in the drawings are only the most preferred embodiment of the present invention and do not represent all of the technical idea of the present invention, various modifications that can be replaced at the time of the present application It should be understood that there may be equivalents and variations.

1 is a view showing a partial configuration of a single crystal manufacturing apparatus used for the implementation of the melting method of the solid raw material for single crystal growth according to a preferred embodiment of the present invention, Figures 2 and 3 according to a preferred embodiment of the present invention It is a figure for demonstrating the melting method of the solid raw material for single crystal growth.

Referring to FIG. 1, the single crystal manufacturing apparatus includes a quartz crucible 10 accommodating a solid raw material for single crystal growth, a crucible housing for enclosing an outer circumferential surface of the quartz crucible 10 and supporting the quartz crucible 10 in a constant shape ( 20), the crucible rotating means 30, which is installed at the bottom of the crucible housing 20 to raise or lower the quartz crucible 10 while rotating the quartz crucible 10 together with the housing 20, the crucible housing 20 Heater 40 for heating the quartz crucible 10 spaced apart from a side wall of the heater 40 and the heat insulating means 50 installed outside the heater 40 to prevent heat generated from the heater 40 from leaking outside. ).

In addition to the configuration shown in the drawing, the single crystal manufacturing apparatus, while dipping the seed crystal seed with a melt (M) in which the solid raw material contained in the quartz crucible 10 is melted in the liquid phase, while rotating in a predetermined direction. Single crystal pulling means for pulling upward to grow single crystal ingot, heat shield means for shielding external emission of heat emitted from the ingot for temperature gradient control at the solid-liquid interface, and forming melt and melt gap, inert gas (e.g. And inert gas supply means for supplying Ar gas).

Since each component of the single crystal manufacturing apparatus is a typical component of the single crystal manufacturing apparatus using the CZ method well known in the art, a detailed description of each component will be omitted.

The melting method of the solid raw material for single crystal growth according to the preferred embodiment of the present invention includes a solid raw material filling step, a first half melting step and a second half melting step.

In the solid raw material filling step, as shown in FIG. 2, the solid raw material S for single crystal growth is filled in the quartz crucible 10. Here, the solid raw material (S) includes polycrystalline silicon and impurities. However, since the present invention is not limited to the type of the solid raw material (S), that is, the melt (M), the type and composition of the solid raw material (S) is different depending on the type of semiconductor single crystal grown by the CZ method. Do.

When the progress of the solid raw material filling step is completed, the first half melting step and the second half melting step proceeds sequentially.

In the first half melting step, a solid raw material is heated by heating the quartz crucible 10 while the quartz crucible 10 is positioned so that the bottom B position of the quartz crucible 10 corresponds to the lower part of the heater 40. It is a melting process to melt.

The second half melting step proceeds to a subsequent process of the first half melting process, and when the solid raw material contained in the quartz crucible 10 is melted, the quartz crucible 10 is disposed such that the melt surface ML position corresponds to the top of the heater 40. It is a melting process of heating the quartz crucible 10 in the state where it is located.

Hereinafter, the first half melting step and the second half melting step will be described in more detail.

According to an embodiment of the present invention, in the first half melting step, the quartz crucible 10 is lowered from the heater such that the position of the bottom B of the quartz crucible 10 is located at a point of 0 to 1 / 4L based on the length L of the heater. Place it in Here, the position of the quartz crucible 10 is moved using the crucible rotating means (see 30 in FIG. 1). In this case, the temperature distribution formed in the quartz crucible 10 is higher in the quartz crucible 10 and the temperature of the quartz crucible 10 is relatively higher than that of the quartz crucible 10 located at the top of the heater 40 in the later melting step. The lower part of the crucible 10 has a relatively low temperature. In addition, the temperature difference between the top and bottom of the quartz crucible 10 becomes relatively low. In addition, the amount of heat applied to the sidewall of the quartz crucible 10, which is vulnerable to deformation, is relatively low compared to when the quartz crucible 10 is positioned above the heater 40 in the later melting step.

When the first half melting process is performed under the positional conditions of the quartz crucible 10 as described above, the temperature distribution applied to the quartz crucible 10 is uniform to prevent the lower portion of the solid raw material S from being more rapidly melted than the upper portion. Can be. As a result, the solid raw material S under the quartz crucible 10 is rapidly melted and the solid raw material S of the unmelted upper portion is depressed to prevent the phenomenon of giving a physical impact to the quartz crucible 10. . As a result, the melting process can be performed stably. In addition, since the amount of heat supplied to the sidewall of the quartz crucible 10, which is vulnerable to thermal deformation, is relatively low as compared with the latter melting step, the quartz crucible 10 may be softened by heat to suppress deformation of the shape. In addition, since the degree of formation of crystalline precipitates in the quartz crucible 10 can be alleviated, it is possible to suppress the causative agent of dielectric dislocation.

The first half melting step is performed until the solid raw material S accommodated in the quartz crucible 10 is entirely melted. Preferably, the first half melting step is performed for a time of 85% to 95% based on the total melting process time.

The second half melting step is a process of activating natural convection of the melt M after the first half melting step is completed to remove defect factors such as bubbles from the melt M, and to homogenize and stabilize the melt M. In the latter melting step, as shown in FIG. 3, the quartz crucible 10 is positioned such that the position of the melt surface ML accommodated in the quartz crucible 10 is 3 / 4L to 1L based on the length L of the heater. ) Is positioned above the heater 40. Here, the position of the quartz crucible 10 is moved using the crucible rotating means (see 30 in FIG. 1). In this case, the temperature distribution formed in the quartz crucible 10 is relatively lower in temperature at the top of the quartz crucible 10 than in the case where the quartz crucible 10 is located under the heater 40 in the first half melting step. The bottom of the quartz crucible 10 is relatively high in temperature. In addition, the temperature difference between the top and bottom of the quartz crucible 10 increases relatively.

When the second half melting process is performed under the positional conditions of the quartz crucible 10 as described above, relatively large thermal energy is applied to the lower portion than the upper portion of the quartz crucible 10. Accordingly, the temperature difference between the upper and lower portions of the melt M accommodated in the quartz crucible 10 becomes larger than when the first half melting step is performed, so that natural convection is activated in the melt M. FIG.

When the natural convection of the melt M is activated, it is possible to completely melt the residual silicon grains remaining fine in the melt M. In addition, bubbles existing in the bottom portion of the quartz crucible 10 move to the melt M surface and are discharged to the outside, thereby effectively removing the factors causing the air pocket.

Preferably, the latter melting step proceeds for a short time of 5% to 15% based on the total melting process time. By shortening the second half melting step, the purpose of the second half melting step can be reduced so that the high temperature heat is applied to the quartz crucible 10 as it is. Therefore, it is possible to minimize the quartz crucible 10 is softened by heat and its shape is deformed. In addition, the crystalline precipitate that causes the dielectric swelling is well formed as the quartz crucible 10 is heated to a high temperature. If the second melting step is short, crystalline precipitates are formed in the quartz crucible 10 to mitigate the phenomenon of peeling. have.

As described above, when the solid raw material filling step, the first half melting step and the second half melting step proceed sequentially, the melting process of the solid raw material for growing the single crystal is completed. 4 is a diagram showing the results of simulation using a commercial program how the vertical and horizontal components of the melt convection change with the position change of the quartz crucible with respect to the heater.

In the figure, the dotted line indicates the maximum heating point of the heater. And (a) is a case where the quartz crucible is placed under the heater to position the maximum heating point of the heater near the surface of the melt, and (b) is a case where the maximum heating point of the heater is placed in the melt by moving the quartz crucible upward. (C) is the case where the quartz crucible is placed on top of the heater so that the bottom portion of the quartz crucible approximately coincides with the maximum heating point of the heater.

Referring to FIG. 4, it can be seen that the convection speed of the vertical and horizontal components of the melt increases as the maximum heating point of the heater moves from the top to the bottom of the quartz crucible. This in turn supports that it is desirable to place a quartz crucible on the upper side of the heater in order to activate natural convection.

Therefore, if the melting process is divided into a first half melting step and a second half melting step as in the present invention, the first half melting step stably melts the solid raw material until most of the solid raw material is melted in a state where natural convection is inactive for a sufficient time. You can. In the latter melting step, natural convection is activated for a short time to effectively remove defect factors such as fine silicon grains or bubbles, and to shorten the time for natural convection to be activated to alleviate the phenomenon of crystalline precipitates being formed and peeled off. Can be.

Hereinafter, the present invention will be described in more detail with reference to experimental examples. The following experimental examples are described for the purpose of helping the understanding of the present invention, and the present invention should not be construed to limit the present invention to terms or experimental conditions described in the experimental examples.

Experimental Example 1

The change of temperature distribution in the melt according to the change of the position of the quartz crucible was confirmed by simulation using a commercial program.

Simulation conditions are as follows. First, the amount of polycrystalline silicon filled in the quartz crucible was set to 150 kg. The length of the heater was set to 540 mm and the power of the heater was set to 95 kw. The position of the quartz crucible was changed to 8 levels (A ~ H). In the first level (A), the bottom position of the quartz crucible was approximately coincident with the lower end of the heater, and then the quartz crucible was raised by 40 mm for each level. At the last level (H), the melt surface position of the quartz crucible was approximately coincident with the top of the heater. The program used was FEMAG (CZ process-specific analysis program), and the temperature distribution formed in the quartz crucible and the melt under the same conditions was calculated.

5 is a view visually showing the temperature distribution change of the quartz crucible and the melt according to the change in position of each level of the quartz crucible through color change, and FIG. Figure 7 is a graph showing the temperature change of the melt bottom according to the positional change of the level of the quartz crucible, Figure 8 shows the temperature difference of the melt surface and the bottom according to the positional change of the level of the quartz crucible One graph.

First, referring to FIG. 5, it can be seen that the temperature of the melt near the quartz crucible sidewall and the bottom increases and the temperature of the melt surface decreases toward the H level. This temperature change can be seen through the color change. For reference, when the red concentration increases, the temperature increases, and when the green concentration increases, the temperature decreases. Such a change in the visual temperature distribution can be quantitatively confirmed through FIGS. 6 and 7. That is, it can be seen that the surface temperature of the melt gradually decreases as it goes from the A level to the H level, and the bottom temperature of the melt increases gradually as it goes from the A level to the H level. 8, it can be seen that the temperature difference between the melt surface and the bottom portion decreases toward the A level while the temperature difference between the melt surface and the bottom portion increases toward the H level. More specifically, at the A level, the temperature difference between the surface and the bottom of the melt was about 50 ° C., but it can be seen that the temperature difference increases to about 330 ° C. as it moves to the H level.

From the above experimental results, the following points can be confirmed. That is, when the solid raw material is melted for a sufficient time while the quartz crucible is placed in the lower part of the heater as in the first half melting step of the present invention, since the variation in the temperature distribution formed on the upper and lower part of the quartz crucible is small, It is possible to stably melt the solid raw material by preventing the raw material from being rapidly melted. In addition, natural convection of the melt for a short time in a state in which the quartz crucible is placed on top of the heater as in the latter melting step of the present invention causes melting of fine silicon grains, removal of air bubbles, and dielectric dislocation. It is possible to reduce the formation and peeling of the crystalline precipitates to be prevented to reduce the yield of the single crystal due to the melting process.

Experimental Example 2

Comparative example

After 150 kg of polycrystalline silicon was filled into a quartz crucible, the polycrystalline silicon was melted by a conventional melting process. Since the melting of the polycrystalline silicon was carried out under the conventional melting conditions, the position of the quartz crucible was fixed to the position of 3 / 4L based on the heater length L and did not move during the melting process.

Example

After 150 kg of polycrystalline silicon was filled into a quartz crucible, the polycrystalline silicon was melted by a melting process according to the present invention. First, the melting process was performed for 6 hours and 30 minutes while the bottom of the quartz crucible was positioned at 4 / 5L based on the heater length L. Then, the melting process was performed for 1 hour while the melt surface was positioned at the 1 / 5L point based on the heater length L. At this time, all other conditions except the position of the quartz crucible were performed in the same state as the comparative example.

The time taken for the complete melting of the polycrystalline silicon by the melting process proceeded according to the comparative example and the Example was about 10 hours, the Example was about 7 hours 30 minutes, the time taken for the example to completely melt the polycrystalline silicon Reduced to 2 hours 30 minutes.

9 is a photograph observing the surface state of the quartz crucible after the melting process according to the comparative example and the embodiment. As shown in FIG. 9, in the case of the embodiment, the quartz crucible was hardly deformed and the formation of crystalline precipitates was remarkably alleviated by shortening the melting process time by more efficiently utilizing the same amount of heater heat. have. If the formation of crystalline precipitates is relaxed, the delamination of crystalline precipitates can also be relaxed. Therefore, it is possible to prevent a decrease in yield of single crystals due to dielectric dislocation caused by crystalline precipitates.

As described above, although the present invention has been described by way of limited embodiments and drawings, the present invention is not limited thereto and is intended by those skilled in the art to which the present invention pertains. Of course, various modifications and variations are possible within the scope of equivalents of the claims to be described.

The following drawings, which are attached to this specification, illustrate preferred embodiments of the present invention, and together with the detailed description of the present invention serve to further understand the technical idea of the present invention, the present invention includes the matters described in such drawings. It should not be construed as limited to.

1 is a view showing a part of the configuration of the single crystal manufacturing apparatus used for the implementation of the melting method of the solid raw material for single crystal growth according to a preferred embodiment of the present invention.

2 and 3 are diagrams for explaining a melting method of a solid raw material for growing a single crystal according to a preferred embodiment of the present invention.

4 is a diagram showing the results of simulation using a commercial program how the vertical and horizontal components of the melt convection change with the position change of the quartz crucible with respect to the heater.

FIG. 5 is a diagram visually showing a change in temperature distribution of the quartz crucible and the melt through color change according to the positional change of the level of the quartz crucible. FIG.

6 is a graph showing the temperature change of the melt surface according to the positional change of the level of the quartz crucible.

7 is a graph showing the temperature change of the bottom of the melt according to the positional change of the level of the quartz crucible.

8 is a graph showing changes in temperature difference between the melt surface and the bottom according to the positional change of the level of the quartz crucible.

9 is a photograph observing the surface state of the quartz crucible after the melting process according to the comparative example and the embodiment.

Claims (5)

A method of melting a solid raw material accommodated in a quartz crucible in a single crystal manufacturing apparatus using a Czochralski method comprising a quartz crucible containing a solid raw material and a heater provided around the quartz crucible sidewall, (a) filling the quartz crucible with a solid raw material; (b) melting the solid raw material by heating the quartz crucible with the quartz crucible positioned so that the bottom position of the quartz crucible corresponds to the lower part of the heater; And (c) heating the quartz crucible with the quartz crucible positioned so that the melt surface position corresponds to the upper portion of the heater when the solid raw material contained in the quartz crucible is melted, Melting of the solid raw material for the single crystal growth, characterized in that step (b) is performed for a relatively longer time than step (c). The method of claim 1, In the step (b), the melting method of the solid raw material for single crystal growth, characterized in that for adjusting the position of the quartz crucible so that the bottom position of the quartz crucible is between 0 ~ 1 / 4L based on the length L of the heater. The method of claim 1, In the step (c), the melting method of the solid raw material for single crystal growth, characterized in that for adjusting the position of the quartz crucible so that the position of the surface of the melt is between 3 / 4L ~ 1L based on the length L of the heater. The method of claim 1, In step (b), Melting method of the solid raw material for the single crystal growth, characterized in that for proceeding for 85% to 95% of the time based on the total melting process time. The method of claim 1, In step (c), Melting method of a solid raw material for growing a single crystal, characterized in that for 5 to 15% of the time based on the total melting process time.

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