JP2009234879A - Single crystal production apparatus by floating zone melting method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a single crystal production apparatus by a floating zone melting method, which can easily measure a geometric quantity of a melting zone necessary for control by a simple configuration. <P>SOLUTION: The single crystal production apparatus is equipped with a first camera 18 provided to detect upper geometric quantities (length L1, material diameter Dp) by substantially aligning the optical axis to a first horizontal plane H1 including an upper outer rim P1 of an induction heating coil 16, a second camera 20 provided to detect lower geometric quantities (length L2, crystal diameter Ds) by substantially aligning the optical axis to a second horizontal plane H2 including a lower outer rim P2 of the coil, and a third camera 22 detecting geometric quantities (length L3 and diameter) of a melt part 11 through a gap between a single crystal 12 and the induction heating coil 16 from an oblique lower direction. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an apparatus for producing a single crystal by a floating zone melting method.

  A floating zone melting method (Floating Zone: FZ method) is conventionally known as a method for growing and manufacturing a single crystal ingot used for semiconductor production. In this floating zone melting method, a polycrystalline silicon rod, which is a material of single crystal silicon, is held vertically, and the polycrystalline silicon rod is partially heated using a high frequency induction heating coil (hereinafter referred to as induction heating coil). By melting and moving the melt zone from the bottom to the top or from the top to the bottom, a high-purity single crystal with few impurities is obtained.

  Specifically, in the floating zone melting method, first, a single crystal silicon rod as a seed crystal is erected from below in a vertical apparatus tube, and a polycrystalline silicon rod as a material is suspended from above. And both the front-end | tips are joined and this junction part is penetrated in the induction heating coil.

  Next, the joined portion is heated directly from the outside to be melted, and the entire crystal is rotated and gradually moved downward to move the melted portion relatively upward. Thus, the polycrystalline silicon rod is monocrystallized from the lower side.

  Then, the crystal is grown in a conical shape until a predetermined diameter is reached, and the diameter is maintained constant after reaching the predetermined diameter. Before the growth is completed, the diameter is gradually reduced, and the completed single crystal silicon rod and the polycrystalline silicon rod of the material are cut off.

  Therefore, during this time, the voltage applied to the induction heating coil oscillator and the moving speed and rotational speed of the single crystal silicon rod and polycrystalline silicon rod should be set appropriately so that the melted portion does not extend excessively and does not melt away. Need to control.

  Therefore, conventionally, the melting part is imaged by an imaging means such as a CCD camera (TV camera), the captured content is taken into a computer and analyzed, and an image change of the melting part is captured, and the control is performed according to the result. Attempts have been made to automate the process.

  As a conventional technique using such a television camera, various techniques are also provided in which a television camera is installed horizontally next to the induction heating coil in order to capture an image of the melted portion by an imaging means.

  However, because the melting part is located in the induction heating coil, the melting part is hidden behind the heating coil particularly in the initial stage of crystal growth, and the melting part cannot be sufficiently captured in the field of view of the TV camera. There is a problem that it becomes difficult to control based on the imaging result of the melted part.

In order to solve such problems, for example, a technique according to Patent Document 1 is known as another conventional technique using a television camera. That is, in addition to the basic configuration as described above, this prior art includes a first television camera installed obliquely above the induction heating coil, a second television camera installed obliquely below the induction heating coil, and induction heating. A third TV camera installed horizontally next to the melting zone (melting zone) located at the bottom of the coil and moving vertically within a range substantially corresponding to the zone length of the melting zone, and horizontally next to the induction heating coil And a fourth TV camera installed, and an image processing circuit is individually connected to each TV camera. The third television camera is attached to a vertical movement device, and the vertical movement device is configured to reciprocate vertically based on the set value of the zone length.
Japanese Patent No. 4016363

  However, in the prior art disclosed in Patent Document 1, it is necessary to provide a vertical movement device for reciprocating the third television camera vertically, which complicates the device configuration and control and increases the cost of the device. There was a problem that it would.

  In addition, since the television cameras are arranged obliquely above and below, and geometric quantities such as the material diameter, crystal diameter, and zone length of the melted part are measured, the measurement results obtained from both cameras are naturally different. For this reason, there is a problem that it is necessary to correct a measurement result caused by a difference in the arrangement position of the cameras, and the control becomes complicated.

  The present invention has been made in view of the above, and provides a single crystal manufacturing apparatus by a floating zone melting method that can easily measure a geometric amount of a melting zone necessary for control with a simple configuration. With the goal.

  In order to achieve the above object, (1) the present invention forms a melting zone by melting a part of a polycrystalline material arranged along the vertical direction with an induction heating coil arranged horizontally, The single crystal is grown by moving the crystallized single crystal relative to the induction heating coil, the geometric amount of the melting zone is detected by an imaging means, and the geometric amount detected by the imaging means By adjusting one or more of the electric power supplied to the induction heating coil according to, the moving speed in the axial direction of the polycrystalline material or the single crystal, the rotational speed of the polycrystalline material or the single crystal, A single crystal manufacturing apparatus using a floating zone melting method for manufacturing the single crystal by controlling a zone length and a crystallized crystal diameter of the melting zone to be constant, wherein the imaging unit includes an upper outer periphery of the induction heating coil. First A first imaging means provided so as to be able to detect an upper geometric amount that is a geometric amount of the upper melting zone including the first horizontal plane by making the optical axis substantially coincide with the horizontal plane; and the induction heating coil A lower geometric amount that is a geometric amount of the melting zone below the second horizontal plane including the second horizontal plane can be detected by making the optical axis substantially coincide with the second horizontal plane including the lower outer peripheral edge of the second horizontal plane. And 2 imaging means.

  According to the invention of (1), the first imaging means can measure the diameter of the polycrystalline material in all steps, and can measure the upper geometric amount of the melting zone. Further, the crystallized crystal diameter can be measured by the second imaging means, and the lower geometric amount of the melting zone can be measured. That is, the geometric amount of the melting zone necessary for control can be easily measured with a simple configuration.

  (2) In the invention of (1), the imaging means further includes third imaging means for detecting a geometric amount of the melting zone through a gap between the single crystal and the induction heating coil from an oblique direction. preferable.

  According to the invention of (2), the third imaging means can measure the crystallized crystal diameter and the melt part diameter in the initial stage of the taper process from the drawing process that could not be accurately measured by the induction heating coil. it can.

  (3) In the invention described in (1) or (2), an optical path conversion unit that converts the optical path for detecting the upper geometric amount and the optical path for detecting the lower geometric amount in a predetermined direction is provided. It is preferable.

  According to the invention of (3), the installation space in the horizontal direction can be reduced by converting the optical path in the horizontal direction into a predetermined direction (for example, the direction perpendicular to the lower side). Can be increased.

  ADVANTAGE OF THE INVENTION According to this invention, the single crystal manufacturing apparatus by the floating zone melting method which can measure easily the geometrical amount of a melting zone required for control with a simple structure can be provided.

Below, the single crystal manufacturing apparatus (henceforth a single crystal manufacturing apparatus) by the floating zone melting method which concerns on this invention is demonstrated in detail based on drawing. In addition, this invention is not limited by this embodiment.
[First Embodiment]
The configuration of the single crystal manufacturing apparatus according to the first embodiment will be described with reference to FIGS. 1 and 2. Here, FIG. 1 is a side view schematically showing the configuration of the single crystal manufacturing apparatus according to the first embodiment, and shows the crystal state in the initial stage of the taper process. FIG. 2 is an explanatory diagram showing measurement points (geometric amounts) and control parameters of the melting zone in the drawing process.

  In this specification, in the process of refining a single crystal, the process of growing the crystal to several tens of millimeters with a diameter of several millimeters in order to make the crystal dislocation-free is called a drawing process, and the diameter of the single crystal is gradually expanded to a predetermined diameter. This process is referred to as a taper process.

<Description of overall configuration>
The single crystal manufacturing apparatus, for example, attaches and holds a polycrystalline silicon material 10 of a silicon rod arranged along the vertical direction to an upper shaft (not shown) positioned directly above the polycrystalline material 10 and also seeds 14 as a single crystal. Is mounted and held on a lower shaft (not shown) located directly below the polycrystalline material 10. Each of the upper shaft and the lower shaft is configured to be rotatable and configured to be able to be fed in the vertical direction.

  The single crystal manufacturing apparatus surrounds the polycrystalline material 10 by the high frequency induction heating coil 16 and melts it to form a melt part (melting zone) 11. Further, the single crystal manufacturing apparatus rotates the polycrystalline material 10 and the single crystal 12 (the seed crystal 14 in the drawing process) after the seed crystal 14 is fused to the melt part 11 and descends in the axial direction. A single crystal (crystallized single crystal) 12 is grown from the melt portion 11.

  The induction heating coil 16 is formed in a substantially annular shape. The oscillation voltage to the induction heating coil 16 is output by a high frequency oscillator (not shown).

Here, for convenience of explanation, the horizontal surface that is the upper surface of the induction heating coil 16 and includes the upper outer peripheral edge P1 is referred to as a first horizontal surface H1. In addition, a virtual horizontal plane including the lower outer peripheral edge P2 of the induction heating coil 16 is referred to as a second horizontal plane H2.
The geometric amount of the upper melt portion 11 including the first horizontal plane H1 is referred to as an upper geometric amount, and the geometric amount of the lower melt portion 11 including the second horizontal plane H2 is referred to as a lower geometric amount. .

<Definition of geometric quantities>
Next, the geometric amount that is a measurement target will be described. The zone length L shown in FIG. 1 is the length of the melt portion 11 in the vertical direction, and is measured by an imaging means described later. That is, the zone length L is obtained by measuring the distance between the material melting surface 11a and the solid-liquid interface 11b using an imaging means described later.

  Further, the zone length L is a total distance of a distance L1, a distance L2, and a distance L3 described later in the initial stage of the taper process.

  The distance L1 is a distance from the first horizontal plane H1 to the material melting surface 11a, and is one of the upper geometric quantities of the melt part 11. The distance L2 is a distance from the second horizontal plane H2 to the solid-liquid interface 11b, and is one of the downward geometric quantities of the melt part 11.

  The distance L3 is a distance corresponding to the thickness of the induction heating coil 16. Further, the diameter of the straight body part of the melt part 11 corresponding to the distance L3 portion is also included in the geometric amount.

  The material diameter Dp is the diameter of the polycrystalline material 10 at the material melting surface 11a. The crystal diameter Ds is a diameter at the solid-liquid interface 11b of the single crystal 12.

  In addition, as shown in FIG. 2, the descending speed of the polycrystalline material 10 is Vp and the rotational speed is Rp. Further, the descending speed of the single crystal 12 (the constricted portion 12a) is Vs, and the rotational speed is Rs.

The zone length L, the material diameter Dp, and the crystal diameter Ds as the geometric quantities described above are detected by a first camera 18, a second camera 20, and a third camera 22 as imaging means described later.
The detection results of the first camera 18, the second camera 20, and the third camera 22 are calculated by an image processing device (not shown).

Then, the electric power supplied to the induction heating coil 16 or the relative movement speed of the polycrystalline material 10 is adjusted according to the detected geometric amount.
Thereby, the zone length L and the crystal diameter Ds of the melt part 11 are controlled to predetermined values, and a single crystal is manufactured.

<Description of imaging means>
The imaging means includes a first camera (first imaging means) 18 provided so that an upper geometric amount can be detected by making the optical axis substantially coincide with the first horizontal plane H1, and the optical axis on the second horizontal plane H2. The second camera (second imaging means) 20 provided so that the lower geometric amount can be detected by substantially matching the two, the single crystal (crystallized single crystal) 12 and the induction heating coil 16 from obliquely below. And a third camera (third imaging means) 22 for detecting the geometric amount of the melt portion 11 through the gap.

  Here, “the optical axis of the first camera 18 substantially coincides with the first horizontal plane H1” means that the optical axis of the first camera 18 coincides with the first horizontal plane H1 within a range in which the upper geometric amount can be detected. It means that Therefore, the actual optical axis deviation at the upper outer periphery P1 is preferably within 8 mm, for example.

  Similarly, “substantially match the optical axis of the second camera 20 with the second horizontal plane H2” means that the optical axis of the second camera 20 matches the second horizontal plane H2 within a range in which the lower geometric amount can be detected. It means that Therefore, the actual optical axis deviation at the lower outer peripheral edge P2 is preferably within 8 mm, for example.

  In addition, the third camera 22 that detects the geometric amount of the melted part 11 through the gap between the single crystal 12 and the induction heating coil 16 from an obliquely downward direction has an angle between the optical axis and a horizontal line of, for example, 5 degrees to 30 degrees. Degree is preferred.

  The third camera 22 can measure the crystal diameter Ds (see FIG. 2) from the drawing process to the initial taper process (until the crystal diameter reaches about 30 mm).

  Further, in the first camera 18, the material diameter Dp can be measured in all steps, and the upper geometric amount (distance L1) of the melt part 11 can be measured.

  Further, in the second camera 20, the crystal diameter Ds is measured from the vicinity where the crystal diameter Ds exceeds, for example, about 30 mm in the taper process, and the downward geometric amount (distance L2) of the melt portion 11 is measured. be able to.

  Therefore, the third camera 22 can photograph the crystal diameter Ds (see FIG. 2) that could not be captured by the conventional horizontal camera 40 (see FIG. 1).

<Description of control>
Next, the aperture control for forming the aperture section 12a (see FIG. 2) will be described.
Based on each geometric amount measured as described above, the voltage applied to the induction heating coil 16 is controlled while keeping the zone length L at an appropriate length.

  That is, the crystal diameter Ds to be crystallized is controlled to a predetermined value by manipulating the amount of heat supplied to the polycrystalline material 10 and changing the melting amount. This is because if the zone length L is too long, the melt portion 11 is cut, and if the zone length L is too short, the melt portion 11 melts down.

Further, the crystal diameter Ds is monitored, and when the deviation from the optimum value is made, the descending speed Vp of the polycrystalline material 10 is finely adjusted. This is because the same zone shape is not obtained for each batch of the manufacturing process depending on the processing accuracy of the top of the polycrystalline material 10 and the use state of the induction heating coil 16.
By controlling in this way, the crystal diameter Ds can be formed to a predetermined diameter.

  As described above, according to the single crystal manufacturing apparatus using the floating zone melting method according to the first embodiment, the geometric amount of the melt part 11 necessary for control can be easily measured with a simple configuration.

  In addition, since the first camera 18 and the second camera 20 are arranged with their optical axes substantially coincided with the first horizontal plane H1 and the second horizontal plane H2, respectively, the geometric amount can be measured directly and accurately. it can.

  Therefore, according to the single crystal manufacturing apparatus according to the first embodiment, the geometric quantities of the polycrystalline material 10, the single crystal 12, and the melt portion 11 can be photographed with a simple configuration in all steps after the drawing step. Can do.

  In the first embodiment, it has been described that the measurement of the crystal diameter Ds (see FIG. 2) from the drawing process to the initial stage of the taper process (until the crystal diameter reaches about 30 mm) is performed by the third camera 22. When only measuring the crystal diameter Ds after the initial stage of the taper process (when the crystal diameter exceeds about 30 mm, for example), the present invention is not limited to this, and the third camera 22 may not be provided.

Although the third camera 22 has been described as being provided obliquely below, the present invention is not limited to this and may be provided obliquely above. In this case, the same effect as described above can be expected.
[Second Embodiment]
In the second embodiment, as shown in FIG. 3, a right-angle prism mirror (optical path conversion means) 30 that converts an optical path for detecting an upper geometric amount and an optical path for detecting a lower geometric amount into a lower right angle direction is provided. In addition, the upper geometric amount and the lower geometric amount can be photographed by one camera 25.

  Here, FIG. 3 is a side view schematically showing the configuration of the single crystal manufacturing apparatus according to the second embodiment. In the following description, members that are the same as or correspond to those already described are denoted by the same reference numerals, and redundant description is omitted or simplified.

  The right-angle prism mirror (optical path conversion means) 30 is a first right-angle prism mirror (optical path conversion means) 30a for converting the optical path for detecting the upper geometric amount in the lower right direction, and the optical path for detecting the lower geometric amount at the lower right angle. A second right-angle prism mirror (optical path conversion means) 30b for converting the direction. Other configurations and control methods are the same as those in the first embodiment.

As described above, according to the single crystal manufacturing apparatus using the floating zone melting method according to the second embodiment, the horizontal installation space can be reduced by converting the optical path in the horizontal direction into the lower right angle direction. Therefore, the degree of freedom in the device design layout can be increased.
Further, since the upper geometric amount and the lower geometric amount can be photographed by one camera 25, the apparatus configuration can be further simplified as compared with the case of the first embodiment.

  In the second embodiment, the description has been given on the assumption that the horizontal optical path is converted downward in the perpendicular direction. However, the present invention is not limited to this, and may be, for example, upward in the perpendicular direction or other directions. The same effect can be expected.

It is a side view which shows typically the structure of the single crystal manufacturing apparatus which concerns on 1st Embodiment. It is explanatory drawing which shows the measurement point and control parameter of the fusion zone in a drawing process. It is a side view which shows typically the structure of the single crystal manufacturing apparatus which concerns on 2nd Embodiment.

Explanation of symbols

10 Polycrystalline material 11 Melt part (melting zone)
11a Material melting surface 11b Solid-liquid interface 12 Single crystal 12a Aperture part 14 Seed crystal 16 Induction heating coil 18 First camera (first imaging means)
20 Second camera (second imaging means)
22 3rd camera (3rd imaging means)
25 Camera 30 Right angle prism mirror (optical path conversion means)
30a First right angle prism mirror (optical path changing means)
30b Second right angle prism mirror (optical path changing means)
Dp Material diameter (geometric amount)
Ds Crystal diameter (geometric amount)
H1 1st horizontal plane H2 2nd horizontal plane L Zone length (geometric amount)
L1 distance (geometric amount)
L2 distance (geometric amount)
L3 distance (geometric amount)
P1 Upper outer periphery P2 Lower outer periphery Vp Lowering speed Rp Rotational speed Vs Lowering speed Rs Rotational speed

Claims (3)

A portion of the polycrystalline material arranged along the vertical direction is melted by an induction heating coil arranged horizontally to form a melting zone, and the polycrystalline material and the crystallized single crystal are relative to the induction heating coil. A single crystal is grown by moving to the position, the geometric amount of the melting zone is detected by an imaging means, and the electric power supplied to the induction heating coil according to the geometric amount detected by the imaging means, By adjusting one or more items of the moving speed in the axial direction of the crystal material or the single crystal and the rotational speed of the polycrystalline material or the single crystal, the zone length and the crystallized crystal diameter of the melting zone are set to a predetermined value. A single crystal manufacturing apparatus by a floating zone melting method for controlling the value to manufacture the single crystal,
The imaging means includes
An upper geometric amount that is a geometric amount of the upper melting zone including the first horizontal plane is provided so as to be detected by substantially matching the optical axis with the first horizontal plane including the upper outer peripheral edge of the induction heating coil. First imaging means provided;
By making the optical axis substantially coincide with the second horizontal plane including the lower outer peripheral edge of the induction heating coil, it is possible to detect a lower geometric amount that is a geometric amount of the lower melting zone including the second horizontal plane. Provided second imaging means;
An apparatus for producing a single crystal by a floating zone melting method.   2. The floating zone according to claim 1, wherein the imaging unit further includes a third imaging unit that detects a geometric amount of the melting zone through a gap between the single crystal and the induction heating coil from an oblique direction. Single crystal manufacturing equipment by melting method.   3. The floating zone melting method according to claim 1, further comprising: an optical path conversion unit configured to convert an optical path for detecting the upper geometric amount and an optical path for detecting the lower geometric amount in a predetermined direction. Single crystal manufacturing equipment.

Images