JP2000233989A - Heater fitting structure for single crystal pulling-up device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent any increase in current density and any discharge from being caused between the seat part and intermediate electrode and also to prevent any damage to the seat part and intermediate electrode from being caused, even when a nut used for fastening intermediate electrode and the seat part loosens by inhibiting decrease in contact area with respect to a heater seat part and a heater intermediate electrode in contact with each other, from being caused, in a heater fitting structure for a single crystal pulling-up device. SOLUTION: In the pulling-up device, a heater 16 is placed in a chamber 13 so as to encircle a crucible for receiving semiconductor melt. As for this structure, the heater 16 is provided with a plurality of leg parts 31 each of which is formed so as to project toward a bottom wall 13a of the chamber 13, and also a seat part 41 formed at the lower end of each of the leg parts 31 so as to horizontally extend, wherein: a male screw part 24b for an intermediate electrode 24, which is formed so as to project from the upper surface of the intermediate electrode 24, is inserted into a hole of the seat part 41 through it and a nut 28 is subjected to screw fitting to the male screw part 24b; the lower end of the intermediate electrode 24 is fitted to the bottom wall 13a of the chamber 13 through a lower electrode 26 and an insulating sleeve 27; thereby the seat part 41 is electrically connected to the lower electrode 26 through the intermediate electrode 24; and further, the upper surface of the intermediate electrode 24 is brought into contact with at least such an area of the lower surface of the seat part, as to contain a point at which a center line G of the corresponding one of the leg parts 31 intersects the lower surface of the seat part 41.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a single crystal pulling apparatus for pulling a semiconductor single crystal from a semiconductor melt stored in a crucible, and more particularly to a heater mounting structure for heating the crucible.

[0002]

2. Description of the Related Art Conventionally, as this type of mounting structure, a heater is provided so as to surround a crucible for storing a semiconductor melt in a chamber, and a pair of graphite intermediate electrodes is connected to the heater, and cooling water is further provided. A heater electrode structure in a single crystal pulling apparatus in which a pair of lower electrodes having passages are respectively coupled to the pair of intermediate electrodes is disclosed (Japanese Patent Laid-Open No. Hei 10-87393). In this electrode structure, the lower electrode has a large-diameter portion in which a concave conical surface is formed on the upper surface and a male screw is formed on the peripheral surface, a small-diameter portion continuously provided at the lower end of the large-diameter portion, and from the small-diameter portion to the large-diameter portion. And a cooling water passage formed and through which cooling water can pass. The intermediate electrode has a large-diameter portion whose lower surface is formed in a convex conical surface corresponding to the concave conical surface, a medium-diameter portion connected to the upper end of the large-diameter portion, and a heater connected to the upper end of the medium-diameter portion. And a small-diameter screw portion that can be inserted into a through hole of a seating portion at the lower end of the leg portion and screwed with a nut. Further, a nut member is fitted into the large-diameter portion of the intermediate electrode, and a seating portion is provided on the inner periphery of the upper end of the nut member so as to be able to be engaged with the shoulder of the large-diameter portion of the intermediate electrode.

A procedure for mounting the heater having the above-described structure will be described. First, the intermediate electrode is placed on the lower electrode in a state where the nut member is fitted into the large diameter portion of the intermediate electrode, and the nut member is screwed into the male screw of the large diameter portion of the lower electrode. As a result, the large-diameter portion of the intermediate electrode is pressed against the large-diameter portion of the lower electrode at the seating portion of the nut member, so that the convex conical surface is in close contact with the concave conical surface and the intermediate electrode is coupled to the lower electrode. Next, the through-hole of the seating portion of the heater is fitted into the small-diameter screw portion of the intermediate electrode, and the nut is screwed into a portion projecting upward from the through-hole of the small-diameter screw portion.

In the heater electrode structure configured as described above, the nut member may be damaged by thermal stress due to thermal expansion of the heater in the radial direction, vibration of the heater, and the like. Joints are not damaged.
That is, even if the nut member is broken, the current supply from the lower electrode to the intermediate electrode is performed through the contact surfaces (the convex conical surface and the concave conical surface) that are in uniform contact with each other, so that the current is locally supplied. Without concentration, the temperature of the cooling water in the cooling water passage does not rise excessively. As a result, no space due to water vapor is generated in the upper part of the cooling water passage, and the joint between the intermediate electrode and the lower electrode is efficiently cooled by the cooling water passing through the cooling water passage, so that the joint is not damaged. Absent.

[0005]

The above-mentioned conventional Japanese Patent Application Laid-Open No.
In the heater electrode structure for pulling a single crystal disclosed in JP-A-87393, the upper surface of the middle diameter portion of the intermediate electrode is smaller than the lower surface of the seating portion of the heater. The structure in which the portion is located, that is, a cantilever structure in which the weight of the heater acts on the protruding tip of the seating portion. For this reason, when the nut screwed into the small-diameter screw portion of the intermediate electrode is loosened due to thermal stress, most of the seating portion rises from the upper surface of the medium-diameter portion, and the contact between the lower surface of the seating portion and the upper surface of the medium-diameter portion is reduced. The area becomes extremely small, the current density becomes extremely large, and a discharge occurs between the raised seat portion and the middle diameter portion, which may damage these members. An object of the present invention is to prevent a decrease in the contact area between the seating portion of the heater and the intermediate electrode even when the nut is loosened, thereby preventing an increase in current density between the seating portion and the intermediate electrode and the occurrence of electric discharge. Another object of the present invention is to provide a heater mounting structure for a single crystal pulling apparatus that can prevent damage to an intermediate electrode.

[0006]

The invention according to claim 1 is
As shown in FIGS. 1 and 4, a heater 16 is provided so as to surround a crucible 12 for storing a semiconductor melt 14 in a chamber 13, and a plurality of legs 31 and 33 are attached to the bottom wall 13 a of the chamber 13. And the legs 31, 33
Seats 41 and 43 are provided at the lower end of the intermediate electrode 24 so as to extend in the horizontal direction. A male screw 24b for the intermediate electrode projecting from the upper surface of the intermediate electrode 24 is inserted through the seats 41 and 43 to form the male screw 24a for the intermediate electrode. , A lower end of the intermediate electrode 24 is attached to the bottom wall 13 a of the chamber 13 via the lower electrode 26 and the insulating sleeve 27,
Reference numerals 1 and 43 denote improvements in the heater mounting structure of the single crystal pulling apparatus electrically connected to the lower electrode 26 via the intermediate electrode 24. The characteristic configuration is that the upper surface of the intermediate electrode 24 is at least the leg portions 31, 33 of the lower surfaces of the seating portions 41, 43.
Are arranged so as to receive the portion including the center line G. In the heater mounting structure of the single crystal pulling apparatus according to the present invention, when the energization and the stop of the heater 16 are repeated, the seating portions 41 and 43 of the heater 16 and the male screw portion 24a for the intermediate electrode are thermally expanded. The heat shrinkage is repeated, and the nut 28 may be loosened due to the thermal stress. At this time, the seating portions 41 and 43 do not bend, and the contact area between the lower surfaces of the seating portions 41 and 43 and the upper surface of the intermediate electrode 24 does not decrease.
The current density flowing between the first electrode 43 and the intermediate electrode 24 does not increase, and no discharge occurs between the seating portions 41 43 and the intermediate electrode 24.

The invention according to claim 2 is the invention according to claim 1, wherein the upper surface of the lower electrode 26 has at least the legs 31, 3 of the lower surface of the intermediate electrode 24, as shown in FIG.
3 and a portion including the center line G, and the insulating sleeve 27
Is configured to receive a portion of the lower surface of the lower electrode 26 that includes the center line G of the legs 31, 33. In the heater mounting structure of the single crystal pulling apparatus according to the second aspect, the lower electrode 26 and the insulating sleeve 2
7 can support the intermediate electrode 24 in a stable state.

[0008] The invention according to claim 3 is the invention according to claim 1 or 2, and further as shown in FIG.
4 receives the entire lower surface of the seating portion 41 and the lower electrode 86.
The upper surface of the lower electrode 86 receives the entire lower surface of the intermediate electrode 84 and the upper surface of the insulating sleeve 87 receives the entire lower surface of the lower electrode 86. In the heater mounting structure of the single crystal pulling apparatus according to the third aspect, the lower electrode 86 and the insulating sleeve 87 can support the intermediate electrode 84 in a more stable state than in the second aspect.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, a first embodiment of the present invention will be described with reference to the drawings. As shown in FIG. 5, a single crystal pulling apparatus 10 is an apparatus for pulling a silicon single crystal 11 by the Czochralski method (CZ method). This device 10
Is a chamber 13 which is an airtight container, and a quartz crucible 12 provided in the chamber 13 for storing a silicon melt 14.
And a quartz crucible 1 installed so as to surround the quartz crucible 12.
And a heater 16 for heating and melting the raw material 15 (silicon polycrystal) in 2 to form a silicon melt 14.

The quartz crucible 12 is formed in a substantially hemispherical shape using quartz. A shaft 19 is erected at the lower center of the chamber 13, and a quartz crucible 12 is provided at the upper end of the shaft 19.
Is provided. The quartz crucible 12 is configured to be able to move up and down via a shaft 19 so that the liquid level of the liquid melt 14 is always kept at a constant level. On the other hand, above the quartz crucible 12 and on the axis of the quartz crucible 12, a wire cable 21 rotatable around the axis and vertically movable is hung. A seed crystal 22 for pulling the silicon single crystal 11 by immersion in 14 is attached.

The heater 16 is, as shown in FIGS.
A heater body 23 formed in a substantially cylindrical shape, four first to fourth legs 31 to 34 projecting from the lower end of the heater body 23 at equal intervals, and lower ends of these legs 31 to 34 And four first to fourth seating portions 41 to 44 provided to extend in the horizontal direction, respectively. The heater main body 23 is formed with a plurality of slits 23a that are alternately cut from the upper edge and the lower edge and extend downward and upward, respectively. The first to fourth seating portions 41 to 44 project inward in the radial direction of the heater main body 23. Is established. The first to fourth seats 41 to 44 have through holes 41a.
To 44a are respectively formed. In this embodiment, a DC voltage is applied to the first seating portion 41 and the third seating portion 43 which are opposed to each other, so that a current flows as indicated by a solid arrow in FIG. Since the mounting structure of the first seat portion 41 and the third seat portion 43 to the bottom wall 13a of the chamber 13 is the same, the mounting structure of the first seat portion 41 is shown as a representative, and the mounting structure of the third seat portion 43 is shown. Is omitted. In addition,
The second and fourth seats 42, 44 are attached to the bottom wall 13a of the chamber 13 via an electrically insulating member (not shown).

As shown in FIGS. 1 and 2, the first seating portion 41 includes an intermediate electrode 24, a lower electrode 26, and an insulating sleeve 27.
Is attached to the bottom wall 13a of the chamber 13 through the hole. The intermediate electrode 24 is formed in a columnar shape from graphite having relatively high conductivity, excellent heat resistance, and less likely to cause crystal contamination. At the center of the lower surface of the intermediate electrode 24, a screw hole 24a whose center line coincides with the axis of the intermediate electrode 24 is formed.
In the center of the upper surface of the intermediate electrode 24, a male screw portion 24b for the intermediate electrode
Are protruded upward. Male thread 2 for this intermediate electrode
When the through hole 41a of the first seat portion 41 is fitted into 4b,
The upper surface of the intermediate electrode 24 is configured to receive a portion of the lower surface of the first seating portion 41 that includes at least the center line G of the first leg 31 (a vertical line passing through the center of gravity of the first leg 31). A nut 28 is configured to be screwed into the male screw portion 24b for the intermediate electrode.

The lower electrode 26 is formed of copper, copper alloy, stainless steel, or the like having a relatively high conductivity, and has a large-diameter portion 26a formed in a disc shape and a downwardly directed center of the lower surface of the large-diameter portion 26a. And a lower electrode male screw portion 26c projecting upward at the center of the upper surface of the large diameter portion 26a. The screw hole 24a of the intermediate electrode 24 can be screwed into the male screw portion 26c for the lower electrode. Further, a cooling water passage 26d is formed in the lower electrode 26 through the small diameter portion 26b and the large diameter portion 26a and reaches near the upper end of the male screw portion 26c for the lower electrode. Be composed.

The insulating sleeve 27 is formed of an electrically insulating material, and has a flange portion 27a and a cylindrical portion 27b projecting downward from the lower surface of the flange portion 27a.
The cylindrical portion 27b is configured to be able to be inserted into a through hole 13b formed in the bottom wall 13a of the chamber 13, and the insulating sleeve 27 is configured so that the small diameter portion 26b of the lower electrode 26 can be inserted.
The upper surface of the large diameter portion 26a of the lower electrode 26 is
Receiving at least a portion of the lower surface of the first leg portion 31 including the center line G, and a flange portion 27a of the insulating sleeve 27.
Is configured to receive at least a portion of the lower surface of the large-diameter portion 26a of the lower electrode 26 that includes the center line G of the first leg 31. In this embodiment, the outer diameter of the large diameter portion 26a is formed to be the same as the outer diameter of the intermediate electrode 24, and the outer diameter of the flange portion 27a is formed to be the same as the outer diameter of the large diameter portion 26a. That is, the upper surface of the large diameter portion 26a receives the entire lower surface of the intermediate electrode 24, and the upper surface of the flange portion 27a is
Is configured to receive the entire lower surface. Although not shown, it is preferable to form a wrench on the outer peripheral surface of the intermediate electrode 24 and the outer peripheral surface of the large diameter portion 26a or the small diameter portion 26b.

The procedure for mounting the heater thus constructed will be described with reference to FIG. The bottom wall 13 of the chamber 13
The cylindrical portion 27b of the insulating sleeve 27 is inserted through the through hole 13b of a. First, a lower electrode male screw portion 26 of the lower electrode 26
The screw hole 24a of the intermediate electrode 24 is screwed into c, and the small diameter portion 26b of the lower electrode 26 is inserted through the insulating sleeve 27 in this state. Next, the through hole 41a of the first seating portion 41 of the heater 16 is fitted into the intermediate electrode male screw portion 24b of the intermediate electrode 24, and the intermediate electrode male screw portion 24b projecting upward from the through hole 41a.
Screw 28. As a result, the first seating portion 41 is attached to the bottom wall 13a of the chamber 13 via the intermediate electrode 24, the lower electrode 26, and the insulating sleeve 27, so that the first seating portion 41 is electrically connected to the lower electrode 26 via the intermediate electrode 24. And the lower electrode 26 is electrically insulated from the bottom wall 13 a of the chamber 13 by the insulating sleeve 27.

In the heater mounting structure configured as described above, when the energization and stop of the heater 16 are repeated, the first seating portion 41 of the heater 16 and the male screw portion 24b for the intermediate electrode repeatedly undergo thermal expansion and thermal contraction. Nut 28 due to thermal stress
May loosen. However, the upper surface of the intermediate electrode 24 is at least the first leg 31 of the first seating portion 41 of the heater 16.
, The first seat portion 41 does not bend, and the contact area between the lower surface of the first seat portion 41 and the upper surface of the intermediate electrode 24 does not decrease. As a result, the current density flowing from the first seat portion 41 to the intermediate electrode 24 does not increase, and the first current
Since no discharge occurs between the seat 41 and the intermediate electrode 24, the first seat 41 and the intermediate electrode 24 are not damaged. Since the large diameter portion 26a of the lower electrode 26 and the flange portion 27a of the insulating sleeve 27 have the same outer diameter as the intermediate electrode 24, the large diameter portion 26a and the flange portion 27
a can support the intermediate electrode 24 in a stable state.

FIGS. 6 and 7 show a second embodiment of the present invention. 6 and 7, the same reference numerals as those in FIGS. 1 and 2 indicate the same parts. In this embodiment, the intermediate electrode 84
Receives the entire lower surface of the first seating portion 41 and the lower electrode 8
6, the upper surface of the intermediate electrode 84 receives the entire lower surface of the intermediate electrode 84, the upper surface of the insulating sleeve 87 receives the entire lower surface of the lower electrode 86, and the intermediate electrode male screw portion 24b coincides with the axis of the intermediate electrode 84 together with the screw hole 24a. Be composed. That is, the outer diameters of the large-diameter portion 86a of the intermediate electrode 84, the lower electrode 86, and the flange portion 27a of the insulating sleeve 27 are outside the large-diameter portion of the first embodiment, the large-diameter portion of the lower electrode, and the flange portion of the insulating sleeve. It is formed larger than the diameter. The large diameter portion 86
a and the outer diameter of the flange portion 87 a are formed to be the same as the outer diameter of the intermediate electrode 84.

In the heater mounting structure configured as described above, since the upper surface of the intermediate electrode 84 receives the entire lower surface of the first seating portion 41, the heater can be supported in a more stable state than in the first embodiment. Even if the nut 28 is loosened, the first seat portion 41 is not bent at all. Further, the intermediate electrode 84 and the lower electrode 8
6, the outer diameter of the large diameter portion 86a is larger than that of the first embodiment, so that not only the contact area between the lower surface of the first seating portion 41 and the upper surface of the intermediate electrode 84, but also the upper surface of the intermediate electrode 84 and the large diameter portion 86
a The contact area of the upper surface is also larger than that of the first embodiment,
Large diameter portion 86a from first seating portion 41 via intermediate electrode 84
Of the current flowing through the first embodiment is lower than that of the first embodiment. As a result, no discharge is generated between the first seating portion 41 and the intermediate electrode 84, and the first seating portion 41 and the intermediate electrode 84 are not discharged.
Will not be damaged. Except for the above, the procedure for mounting the heater and the operation of the heater mounting structure are substantially the same as those in the first embodiment, and therefore, the description thereof will not be repeated.

In the first and second embodiments, a silicon single crystal is used as a semiconductor single crystal, but a gallium arsenide single crystal or another semiconductor single crystal may be used.
In the first and second embodiments, the pulling apparatus using the CZ method is described as the single crystal pulling apparatus. However, a continuous charge type magnetic field application choke that applies a magnetic field to the melt to suppress convection of the melt. A pulling device by the Ralski method (CMCZ method), a pulling device by a continuous charge type Czochralski method (CCZ method) without applying a magnetic field, or another pulling device may be used. Further, in the first and second embodiments, the first to fourth seats are provided to project inward in the radial direction of the heater main body. However, the first to fourth seats are directed outward in the radial direction of the heater main body. May be protruded. In the first and second embodiments, four legs are protruded from the lower end of the heater main body. However, two, three, five or more legs may be protruded. Further, in the first and second embodiments, the intermediate electrode is formed in a columnar shape, and the large-diameter portion of the lower electrode is formed in a disk shape. However, the intermediate electrode is formed in a polygonal column shape, and the lower electrode is formed. The large diameter portion may be formed in a polygonal plate shape. In this case, it is not necessary to form a spanner hook on the outer peripheral surface of the intermediate electrode and the large diameter portion.

[0020]

As described above, according to the present invention, the male screw portion for the intermediate electrode projecting from the upper surface of the intermediate electrode is inserted into the seat of the heater, and the nut is screwed into the male screw portion for the intermediate electrode. The lower end of the intermediate electrode is attached to the bottom wall of the chamber via the lower electrode and the insulating sleeve, the seat is electrically connected to the lower electrode via the intermediate electrode, and the upper surface of the intermediate electrode is the lower surface of the seat. Is configured to receive at least a portion including the center line of the leg, the seat does not bend even if the nut is loosened due to thermal stress, and the contact area between the lower surface of the seat and the upper surface of the intermediate electrode does not decrease. As a result, the current density flowing between the seating portion and the intermediate electrode does not increase, and no discharge occurs between the seating portion and the intermediate electrode, so that the seating portion and the intermediate electrode can be prevented from being damaged.

The upper surface of the lower electrode receives at least a portion of the lower surface of the intermediate electrode that includes the center line of the leg, and the upper surface of the insulating sleeve receives the portion of the lower surface of the lower electrode that includes the center line of the leg. With this configuration, the lower electrode and the insulating sleeve can support the intermediate electrode in a stable state. Furthermore, the upper surface of the intermediate electrode receives the entire lower surface of the seat,
If the upper surface of the lower electrode receives the entire lower surface of the intermediate electrode and the upper surface of the insulating sleeve receives the entire lower surface of the lower electrode, the lower electrode and the insulating sleeve support the intermediate electrode in a more stable state than described above. be able to.

[Brief description of the drawings]

FIG. 1 is an enlarged sectional view of a portion A in FIG. 3 including an intermediate electrode and a lower electrode according to a first embodiment of the present invention.

FIG. 2 is a sectional view taken along line BB of FIG. 1;

FIG. 3 is a side view of the heater.

FIG. 4 is a plan view of the heater.

FIG. 5 is a sectional view of a main part of a single crystal pulling apparatus including the heater.

FIG. 6 is a sectional view showing a second embodiment of the present invention and corresponding to FIG. 1;

FIG. 7 is a sectional view taken along line CC of FIG. 6;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Single crystal pulling apparatus 12 Quartz crucible (crucible) 13 Chamber 13a Bottom wall 14 Silicon melt (semiconductor melt) 16 Heater 24,84 Intermediate electrode 24b Male screw part for intermediate electrode 26,86 Lower electrode 27,87 Insulation sleeve 28 Nut 31 first leg portion 33 third leg portion 41 first seat portion 43 third seat portion G center line of first leg portion

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Masayoshi Takemura 1-5-1, Otemachi, Chiyoda-ku, Tokyo F-term in Mitsubishi Materials Silicon Co., Ltd. 4G077 AA02 BA04 BE46 CF10 EG18 EJ02 PE27

Claims (3)

[Claims] A heater (16) is provided so as to surround a crucible (12) for storing a semiconductor melt (14) in a chamber (13), and the heater (16) has a plurality of legs (31, 33). ) Is the chamber (13)
The seats (41, 43) are provided at the lower ends of the legs (31, 33) so as to extend in the horizontal direction, and project from the upper surface of the intermediate electrode (24). Male thread for intermediate electrode (24b)
Is inserted through the seating portion (41, 43), a nut (28) is screwed into the male screw portion (24b) for the intermediate electrode, and the intermediate electrode (24)
Is attached to the bottom wall (13a) of the chamber (13) via a lower electrode (26) and an insulating sleeve (27).
(41, 43) is the lower electrode (26) via the intermediate electrode (24)
In the heater mounting structure of the single crystal pulling device electrically connected to, the upper surface of the intermediate electrode (24) is at least the center line of the leg (31, 33) of the lower surface of the seat (41, 43). A heater mounting structure for a single crystal pulling apparatus configured to receive a portion including (G). 2. The upper surface of the lower electrode (26) receives at least a portion of the lower surface of the intermediate electrode (24) including the center line (G) of the leg (31, 33), and the upper surface of the insulating sleeve (27). Is the lower electrode (2
The heater mounting structure for a single crystal pulling apparatus according to claim 1, wherein the lower surface of (6) is configured to receive a portion including a center line (G) of the leg portion (31, 33). 3. The upper surface of the intermediate electrode (84) receives the entire lower surface of the seat (41), the upper surface of the lower electrode (86) receives the entire lower surface of the intermediate electrode (84), and the insulating sleeve (87). 3. A heater mounting structure for a single crystal pulling apparatus according to claim 1, wherein an upper surface of the heater is configured to receive an entire lower surface of the lower electrode.