JPH037405Y2 - - Google Patents

Description

[Detailed explanation of the idea]

[Industrial Application Field] The present invention relates to an apparatus for growing crystals such as silicon single crystals used as materials for semiconductor devices, for example. [Prior art] There are various methods for growing single crystals.
Among them, there is a rotating pull-up method. In this method, as shown in FIG. 3, the single crystal material inserted into a crucible 13 is completely melted by an induction heating coil or a resistance heating coil 12, and then the molten liquid 14 is pulled up to a pulling rod 1.
In this method, the single crystal 15 formed by solidifying the molten liquid 14 is grown by pulling the molten liquid 14 upward. In this method, a problem arises in that the component elements are segregated in the growth direction of the single crystal 15 because the amount of melt decreases as the crystal grows. To solve this problem, a fused layer method has been proposed. In this method, as shown in FIG. 4, an induction heating coil 12, which is movable up and down outside the crucible 13, is gradually lowered from the upper side of the crucible 13 to the lower side, regardless of the amount of single crystal 15 grown. First, the amount of the melt 14 in the crucible 13 is maintained constant to grow the single crystal 15 (JOURNAL OF THE ELECTROCHEMICAL
SOCIETY.July, 1985, P393-365). [Problems to be solved by the invention] However, although segregation is improved when using the above-mentioned molten layer method, since the heating means of the crystal growth apparatus is an induction heating coil, the induced electromagnetic force causes the molten liquid to Forced convection occurs; for example, if a quartz (SiO ₂ ) crucible is used, the convection causes the quartz crucible to melt and oxygen to elute.
Oxygen is contained in the single crystal. When a silicon wafer obtained by slicing a silicon single crystal containing oxygen in this manner is heat-treated in order to use it as a material for a semiconductor device, crystal defects may occur due to the oxygen content. For this reason, it was not possible to produce a low-oxygen single crystal using the fused layer method. Furthermore, when using the above-mentioned crucible, heat is transferred in the vertical direction, so heat escapes from the upper part where heat is needed to the lower part where it is not needed, resulting in poor heating efficiency. It was difficult to manage. [Means for solving the problem] The present invention was made in view of the above circumstances, and has a structure in which the crucible has two layers, an inner and outer layer, and the outer layer is divided vertically, and By providing a resistance heating type heater, the crystal material inserted into the crucible is melted from the top to the bottom and the molten liquid is pulled upward to prevent segregation and grow crystals. Even if there is a problem, convection of the molten liquid in the crucible can be suppressed to grow crystals with reduced oxygen content, and heat transfer in the vertical direction of the crucible can be suppressed, resulting in excellent heating efficiency and An object of the present invention is to provide a crystal growth apparatus that allows easy control of liquid volume. The crystal growth apparatus according to the present invention is an apparatus for growing crystals by melting a crystal material inserted into a crucible from the upper side to the lower side and pulling the melt upward, and the crystal growth apparatus is an apparatus for growing crystals by pulling the melt upward. In order to prevent heat convection of the melt, a crucible is integrally attached with an outer layer crucible formed by stacking annular crucible bodies vertically, and a plurality of crucibles are provided in the vertical direction around the crucible, and each It is characterized by comprising a resistance heating type heater that can control heating, and a heat shield provided around the heater. [Example] The present invention will be specifically explained below based on the drawings. FIG. 1 is a schematic side sectional view showing an embodiment of the present invention, and numeral 1 in the figure indicates a chamber. The chamber 1 is a substantially cylindrical vacuum container with its axial direction perpendicular, and a rotation shaft 7' of a lifting chuck 7 that rotates at a predetermined speed in the direction of the arrow is passed through the center of the upper surface with an air shield. . A seed (a single crystal serving as a nucleus for crystal growth) 5' is attached to the pulling chuck 7. A support shaft 6 for a crucible 3, which rotates at a predetermined speed in the opposite direction on the same axis as the pulling chuck 7, passes through the center of the bottom surface of the chamber 1 in an air-shielded manner. A crucible 3' made of graphite is attached to the tip of the support shaft 6 with a crucible 3 made of quartz (SiO ₂ ) fitted inside the crucible 3'. The graphite crucible 3' is divided into, for example, five parts in the axial direction, and the upper four stages of annular crucible bodies 31', 3
2', 33', 34' and a bottomed annular crucible body 35' at the bottom, and the bottomed annular crucible body 35' moves the quartz crucible 3 in its radial direction. is prevented. A pipe 9 for adding impurities is provided above the crucible 3, passing through the chamber 1, and a resistance heater 2 is provided outside the rotation range of the crucible 3, and a resistance heater 2 is provided outside the rotation range of the crucible 3, and a Heat shield 8 in position
are arranged in a concentric cylindrical shape. The heater 2 includes resistance heating coils 21, 22, 23, 24, 25, 26, 27 whose axial dimension is sufficiently shorter than the axial dimension of the crucible 3.
For example, seven are provided on the front side wall of the crucible 3 along its axial direction. Each of the resistance heating coils 21, . . . , 27 is connected to a power terminal of a current value control device (not shown), and the current supply/disconnection and current value of each coil 21, etc. are controlled by the current value control device. be done. A case in which a single crystal is grown using the fused layer method using the apparatus of the present invention configured as described above will be described below. For example, the operator first inserts the single crystal material 10 into the crucible 3 and energizes several coils 21 and the like on the upper side of the heater 2 to heat and melt the upper part of the material 10. and the melt 4 in the crucible 3
When it reaches a predetermined amount or a predetermined depth, impurities are added through the tube 9, and then the lifting chuck 7 is lowered once.
After the seed 5' is brought into contact with the melt 4, the chuck 7 is rotated and pulled upward to grow the single crystal 5. While growing the single crystal 5, control is performed to increase the amount of electric power from the upper coil 21 etc. to the lower coil 22 etc. in order to keep the amount or depth of the melt 4 in the crucible 3 constant. During the above-mentioned melting of the material, since the crucible 3 has a structure in which it is divided in the axial direction, the heat transfer coefficient decreases at the joints and the heat flow in the vertical direction of the crucible 3 is blocked. Therefore, when heating with the heater 2 using such a crucible, the crucible 3 to be heated
The temperature was raised only in the vicinity of the part, resulting in high heating efficiency and easy control of the melt at a predetermined amount. The grown crystals are free from segregation, and since they are heated by a resistance heater, convection is less likely to occur in the melt, resulting in a low oxygen level. In the above embodiment, the outer graphite crucible 3'
Although the crucible 3' is divided into five parts, the present invention is not limited to this, and the crucible 3' may be divided into an appropriate number of parts. The heating efficiency is better when the crucible 3' is divided into as many parts as possible, and when such a crucible is used, the amount of melt can be easily controlled. Further, in the above embodiment, for example, seven coils are provided so as to cover the entire side wall of the crucible, but the present invention is not limited to this, and as shown in FIG.
For example, four coils 21', 22', 23', 2
It goes without saying that the heaters 2', each consisting of a set of heaters 4', may be moved up and down outside the crucible 3. Further, although the above embodiment shows a case where the heater is divided, the present invention may be configured to cover the crucible with a single wide heater depending on the case. In order to insert the silicon single crystal material 10 into the crucible 3 and grow it into a single crystal using the molten layer method, the upper side thereof is melted by the heater 2 until a predetermined melt depth is reached, and then the crucible 3 is Rotate at 0.5 rpm, and rotate chuck 7 at 20 rpm in the opposite direction.
The material 10 was pulled up while rotating, and material 10 was melted to grow a silicon single crystal of about 4 m. After starting to melt the material 10, an appropriate amount of P as an impurity was added through the tube 9 at a predetermined pitch. Table 1 shows the results of measuring the resistivity of wafers made by taking samples at 50 mm intervals from the grown silicon single crystal.

【table】

〔effect〕

As detailed above, the present invention is configured to heat the split crucible using a resistance heater.
Since multiple heaters that can individually control the temperature of the crucible are arranged above and below, the temperature gradient inside the crucible can be easily set. Together with the structure, thermal convection of the molten liquid is prevented, resulting in excellent heating efficiency and easy control of the amount of molten liquid. Moreover, no segregation occurs in the grown crystals, and the present invention has excellent effects such as improving the product yield of crystals.

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view showing an embodiment of the present invention;
FIG. 2 is a schematic sectional view showing another embodiment of the present invention, and FIGS. 3 and 4 are explanatory views of a conventional device. 2... Resistance heating type heater, 3... Crucible, 4...
...melt, 5...single crystal, 31', 32', 33',
34', 35'... Crucible element.

Claims (1)

[Scope of Claim for Utility Model Registration] In an apparatus for growing crystals by melting a crystal material inserted into a crucible from the top to the bottom and pulling the melt upward, , a crucible having an integrally attached outer layer crucible formed by stacking annular crucible bodies vertically to prevent thermal convection of the melt, and a plurality of crucibles provided in the vertical direction around the crucible,
A crystal growth apparatus comprising: a resistance heating type heater whose heating can be individually controlled; and a heat shield provided around the heater.