SINGLE CRYSTAL GROWING APPARATUS

Technical Field

[1] Embodiments relate to a single crystal growing apparatus.

Background Art

[2] In semiconductor device manufacturing, silicon wafers that are mainly used as substrates are generally manufactured by forming high purity, polycrystalline silicon, followed by growing a single crystal from the polycrystalline silicon using crystal growing techniques such as the Czochralski(CZ) method or the floating zone(FZ) method to produce a mono-crystalline silicon rod, thinly slicing the rod to produce silicon wafers, polishing one surface of each wafer and cleaning the wafers, and performing a final inspection step.

[3] In single crystal growth where a seed crystal is used to grow a single crystal, a thermal shock occurs when the seed crystal at a low temperature contacts high- temperature silicon melt. The thermal shock causes shear stress within the crystal, and the shear stress causes dislocation within the single crystal.

[4] A necking process is performed during single crystal growth to prevent dislocation.

The necking process is a processing technique for preventing dislocation by drawing a single crystal into a thin, elongated form.

[5] In order to support the heavy weight of a large load, broad diameter single crystal being grown, a necking process of a greater diameter must be performed. When the diameter of a single crystal being grown is made large, however, shear stress is increased, causing an increased rate of dislocation movement within the crystal. Disclosure of Invention Technical Problem

[6] Accordingly, embodiments are directed to a single crystal growing apparatus that reduces shear stress generated in a crystal during a necking process and reduces the rate of dislocation movement within the crystal, to increase crystal diameter in a necking process required for growing single crystals of heavy weight and broad diameter. Technical Solution

[7] In some embodiments, there is provided a single crystal growing apparatus including: a chamber; a crucible provided in the chamber to hold silicon melt; a heater provided in the chamber to heat the crucible; and heat supplying means for supplying heat to a crystal at a necking portion during single crystal growth.

[8] In other embodiments, there is provided a single crystal growing apparatus including: a chamber; a crucible provided in the chamber to hold silicon melt; a heater provided in the chamber to heat the crucible; a heat collecting reflector plate provided in the chamber to collect heat radiated from the silicon melt or the heater and reflect the collected heat to a crystal at a necking portion during single crystal growth; and a heat source provided in the chamber to generate and supply heat to the crystal at the necking portion during the single crystal growth.

Advantageous Effects

[9] A single crystal growing apparatus according to embodiments uses heat supplying means such as a heat collecting reflector plate or a heat source to supply heat to a crystal during a necking process, in order to reduce the rate of dislocation movement within the crystal by lowering temperature differences of the crystal and reducing shear stress generated in the crystal when the necking process is performed.

[10] Accordingly, by enabling reduction in the rate of dislocation movement within a crystal during a necking process, necking processes for greater diameters may be implemented in the future that can support greater weights when growing high load, large diameter single crystals. Brief Description of Drawings

[11] FIG. 1 is a schematic view of a single crystal growing apparatus according to a first embodiment.

[12] FIG. 2 is a perspective view of a first heat supplying unit of the single crystal growing apparatus according to the first embodiment.

[13] FIG. 3 is a sectional view of the first heat supplying unit of the single crystal growing apparatus according to the first embodiment.

[14] FIG. 4 is a schematic view of a single crystal growing apparatus according to a second embodiment.

[15] FIG. 5 is a perspective view of a first heat supplying unit of the single crystal growing apparatus according to the second embodiment.

[16] FIG. 6 is a perspective view of a second heat supplying unit of the single crystal growing apparatus according to the second embodiment.

[17] FIG. 7 is a sectional view of the second heat supplying unit of the single crystal growing apparatus according to the second embodiment.

[18] FIG. 8 is an exemplary view showing shear stress generation results within a single crystal during a necking process with a typical single crystal growing apparatus.

[19] FIG. 9 is an exemplary view showing shear stress generation results within a single crystal during a necking process with a single crystal growing apparatus according to embodiments. Best Mode for Carrying out the Invention [20] Hereinafter, embodiments will be described in detail with reference to accompanying drawings.

[21] For the sake of descriptive convenience and clarity in the description of embodiments, thicknesses and sizes of the respective elements in the drawings may be exaggerated, omitted, or schematically represented. It should also be understood that the depictions of respective elements do not necessarily represent sizes accurately.

[22] <EMBODIMENTS>

[23] FIG. 1 is a schematic view of a single crystal growing apparatus according to a first embodiment.

[24] A silicon single crystal growing apparatus 100 according to the first embodiment may include a chamber 10, a crucible 20, a heater 30, raising means 40, heat supplying means 50, etc.

[25] For example, a single crystal growing apparatus 100 according to the first embodiment may include a chamber 10, a crucible 20 provided within the chamber 10 for holding silicon melt, a heater 30 provided within the chamber 10 for heating the crucible 20, and heat supplying means 50 for supplying heat to the necking portion crystal during single crystal growing.

[26] The chamber 10 provides a predetermined space in which predetermined processes are performed for growing single crystal ingots for silicon wafers that are used as materials for semiconductors and other electronic components. Here, the Czochralsk: CZ method is a representative technique for growing silicon single crystal ingots (IG) by dipping a mono-crystalline seed crystal 1 in melted silicon, and then slowly raising it. According to this method, after a necking process is first performed where a thin, long crystal is grown from the seed crystal 1, a shouldering process is performed to grow the crystal perpendicularly to achieve a target diameter, followed by a body growing process to grow the crystal in a uniform diameter to a predetermined length, and a tailing process that ends crystal growth by gradually reducing the diameter of the crystal.

[27] A radiation insulator 11 may be installed on the inner wall of the chamber 10 to prevent heat from the heater 30 (to be described) from escaping through the sidewall of the chamber 10.

[28] In embodiments, various factors such as rotation of a quartz crucible and inner pressure conditions may be controlled to control oxygen concentration during silicon single crystal growth. For example, in order to control oxygen concentration in embodiments, argon gas may be injected into the chamber 10 of the silicon single crystal growing apparatus and the chamber 10 may be exhausted at the bottom.

[29] The crucible 20 may be provided within the chamber 10 to hold silicon melt (SM), and may be formed of quartz material. A crucible support 21 formed of graphite may be provided at the outside of the crucible 20 to support the crucible 20. The crucible support 21 may be fixedly installed on a rotating shaft 23, and the rotating shaft 23 may be rotated by driving means (not shown) to rotate the crucible 20 and may raise and lower the crucible 20 to maintain the surface of the high-temperature melt at the same height.

[30] The heater 30 may be provided within the chamber 10 to heat the crucible 20. For example, the heater 30 may be cylindrically formed to enclose the crucible support 21. The heater 30 heats an ultrapure, mono-crystalline silicon chunk loaded in the crucible 20 to produce silicon melt (SM).

[31] The raising means 40 may be installed at the top of the chamber 10 to wind a cable

41 and perform raising. A seed crystal 1 may be installed at the bottom of the cable 41 in order to grow a single crystal ingot (IG) when contacted with silicon melt (SM) within the crucible 20 and raised. During growth of a single crystal ingot (IG), the raising means 40 may perform raising by rotating and winding the cable 41. Here, the silicon single crystal ingot (IG) may be centered on the same axis as the rotating shaft 23 of the crucible 20, and may be rotated in the direction opposite to the rotating direction of the crucible 20 while being raised.

[32] FIG. 2 is a perspective view of a first heat supplying unit of the single crystal growing apparatus according to the first embodiment, and FIG. 3 is a sectional view of the first heat supplying unit of the single crystal growing apparatus according to the first embodiment, taken along line A-A.

[33] The heat supplying means 50 may supply heat to a crystal in a necking portion 5 to reduce the rate of dislocation movement within the crystal by reducing shear stress generated in the crystal at the necking portion 5 from thermal shock during silicon single crystal growth.

[34] The heat supplying means 50 may include a first heat supplying unit 51 that collects and supplies heat radiated from silicon melt (SM) or a heater 30 to a necking crystal in order to reduce temperature difference of the crystal.

[35] The first heat supplying unit 51 may include a heat collecting reflector plate

(reference numeral 51 below) formed in a shape that encloses the periphery of the necking crystal.

[36] The heat collecting reflector plate 51 may be formed in a circular cone shape, polygonal cone shape, or one of various other shapes, and may be formed with a diameter of 300mm or less when considering typical diameters for single crystal growth, but is not limited to this diametric range.

[37] Also, the heat collecting reflector plate 51 may be applied at a sloped angular range between 15° and 75° in order improve crystallization during a necking process, but is not limited thereto. [38] Many types of materials such as graphite (with good heat absorption) and molybdenum (with high reflectivity) may be applied to the heat collecting reflector plate 51.

[39] A cable through-hole 50a may be defined in the center of the heat collecting reflector plate 51, through which the cable 41 that raises the seed crystal 1 may pass.

[40] The heat collecting reflector plate 51 may be disposed above the crucible 20. For example, the heat collecting reflector plate 51 may be disposed at the upper portion of the seed crystal 1, and may be raised and lowered in connection with the seed crystal 1 by the raising means 40 that raises and lowers the seed crystal 1.

[41] FIG. 4 is a schematic view of a single crystal growing apparatus according to a second embodiment, FIGS. 5 and 6 are perspective views of first and second heat supplying units of the single crystal growing apparatus according to the second embodiment, and FIG. 7 is a sectional view of the second heat supplying unit of the single crystal growing apparatus according to the second embodiment, taken along line B-B.

[42] Referring to FIGS. 4 through 7, a single crystal growing apparatus 200 according to the second embodiment may include a chamber 10, a crucible 20, a heater 30, raising means 40, and heat supplying means 50.

[43] Technical features of the first embodiment may be employed by the second embodiment.

[44] For example, the heat supplying means 50 of the second embodiment may include a heat source 52 in addition to the heat collecting reflector plate 51 of the first embodiment. Below, like reference numerals will used for elements having the same functions as those in the first embodiment, and detailed description thereof will be omitted.

[45] The heat supplying means 50 may include a first heat supplying unit 51 that collects heat radiated from silicon melt (SM) or a heater 30 during single crystal growth and supplies the heat to a necking crystal, and a second heat supplying unit 52 that supplies self-generated heat to the necking crystal.

[46] The first heat supplying unit 51 may include a heat collecting reflector plate 51 provided in a shape enclosing the periphery of a necking crystal at the upper portion of a seed crystal 1, for collecting heat radiated from silicon melt (SM) or a heater 30 and supplying the heat to the necking crystal.

[47] The second heat supplying unit 52 may include a heat source (represented by reference numeral 52 below) of which at least one is provided on the heat collecting reflector plate 51, for supplying self-generated heat to the necking crystal.

[48] The heat source 52 may be formed in any of various forms attached to the un- dersurface of the heat collecting reflector plate 51.

[49] For example, as shown in FIG. 5, a first heat source 52a may be provided integrally around the peripheral undersurface of the heat collecting reflector plate 51.

[50] Also, as shown in FIG. 6, a second heat source 52b may be formed in an approximately triangular shape provided in plurality on the undersurface of the heat collecting reflector plate 51. While the configuration of the plurality of triangular second heat sources 52b in embodiments is given as an example, it is not limited thereto and may include any of various other shapes including circular, elliptical, and polyhedral shapes.

[51] While not shown in the drawings, the heat source 52, being an element that supplies self-generated heat to a necking crystal, may be disposed at the upper portion of the seed crystal 1, and may be formed in a circular cone shape or a polygonal cone shape that encloses the periphery of the necking crystal.

[52] The single crystal growing apparatuses 100 and 200 thus configured in the above embodiments may increase the diameter of a crystal during a necking process by lowering the rate of dislocation movement within the crystal through reducing shear stress generated in the necking portion 5 of the crystal during single crystal growth.

[53] While methods of reducing the temperature of crystal or reducing its temperature difference may be proposed as an improvement to reduce shear stress within the crystal during a necking process, because the temperature reduction method is virtually impossible due to the crystal being in contact with silicon melt (SM), the approach for reducing crystal temperature difference must be taken.

[54] Specifically, in order to reduce the temperature difference of crystal during a necking process, the single crystal growing apparatuses 100 and 200 according to embodiments absorb heat from silicon melt (SM) or a heater 30 and transfer the heat to the crystal or generate heat to transfer to the crystal.

[55] In further detail, a circular cone-shaped or polygonal cone-shaped heat collecting reflector plate 51 that encloses the periphery of a crystal is provided to collect heat from silicon melt (SM) or radiated from a heater 30 and supply the heat to the crystal, or supply heat generated by a heat source 52 to the crystal, during a necking process. By thus supplying heat to the crystal during a necking process, temperature difference of the crystal may be reduced. Accordingly, thermal shock arising from temperature difference of the crystal may be reduced, lowering shear stress incidence within the crystal, so that the rate of dislocation movement within the crystal may be reduced.

[56] FIG. 8 is an exemplary view showing shear stress generation results within a single crystal during a necking process with a typical single crystal growing apparatus, and FIG. 9 is an exemplary view showing shear stress generation results within a single crystal during a necking process with a single crystal growing apparatus according to embodiments.

[57] According to test results shown in FIG. 8 in which a typical single crystal growing apparatus is applied, the shear stress that occurs within a crystal during a necking process is about 2.5E6N/m ² . In comparison, FIG. 9 shows the application of single crystal growing apparatuses 100 and 200 according to embodiments, where the shear stress that occurs within a crystal during a necking process is about 1.7E6N/m ² .

[58] Specifically, because the single crystal growing apparatuses 100 and 200 according to embodiments employ a heat supplying unit 50 such as a heat collecting reflector plate 51 or a heat source 52 to supply heat to a crystal during a necking process in order to reduce thermal shock from a temperature difference of the crystal, shear stress can be reduced by about O.8E6N/m ² from that of typical apparatuses. Therefore, by lowering incidence of shear stress within a crystal at a necking portion 5 during silicon single crystal growth, the rate of dislocation movement within the crystal can be reduced.

[59] Further, because the rate of dislocation movement within a crystal during a necking process can be reduced, necking processes for greater diameters may be implemented in the future that can support greater weights when growing high load, large diameter single crystals.

[60] While the present invention has been described and illustrated herein with reference to preferred embodiments thereof, such description is merely exemplary and does not limit the present invention, and it will be apparent to those having ordinary skill in the art that various modifications and variations can be made therein without departing from the spirit and scope of the invention. For example, each element specifically mentioned in embodiments of the present invention can be modified and worked. Thus, it is intended that the present invention covers the modifications and variations of this invention that come within the scope of the appended claims and their equivalents. Industrial Applicability

[61] Because the rate of dislocation movement within a crystal during a necking process can be reduced by a single crystal growing apparatus according to embodiments, necking processes for greater diameters may be implemented in the future that can support greater weights when growing high load, large diameter single crystals.