JP2010076961A - Method and apparatus for measuring position - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method and an apparatus for measuring the melt surface position (melt level) of a raw material melt in a Czochralski furnace. <P>SOLUTION: The method is for measuring the position of a measurement part 7a wherein the reflected light reflected at the measurement part 7a is condensed by a condensing lens 13a and received by a two-dimensional light sensor 13b and the position of the measurement part 7a is measured by using the principle of triangulation based on the luminance of received reflected light. When the direction where the reflected light shows the position of the measurement part 7a in the two-dimensional light sensor 13b is called the first direction D1 and the direction which intersects perpendicularly with the first direction D1 is called the second direction D2, the method is equipped with the second direction centroid calculation procedure for calculating the second direction centroid which is the centroid of the second wave showing the luminance of reflected light along the second direction D2, the first direction center position calculation procedure for calculating the first direction center position which is the center of the first wave showing the luminance of reflected light along the first direction D1 based on the second direction centroid and the measurement part calculation procedure for calculating the position of the measurement part based on the first direction center position. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention uses a triangulation principle and a position measuring method and a position measuring apparatus for measuring a measurement location of a Czochralski furnace in a single crystal pulling apparatus, for example, a position (melt level) of a raw material melt. About.

  The Czochralski method (hereinafter also referred to as “CZ method”) is a method of using silicon contained in a crucible (crucible) provided in a Czochralski furnace (hereinafter also referred to as “CZ furnace”) in a single crystal pulling apparatus. This is a method of pulling up a single crystal ingot while growing it from a raw material melt. In order to grow single crystals with good controllability, it is necessary to accurately measure the position of the melt surface (hereinafter also referred to as “melt level”) and adjust the melt level to match the growth of the single crystal. is there.

  In particular, in a silicon single crystal pulling apparatus using the CZ method, a heat shield is usually provided to control heat radiation from the heater and silicon melt and to rectify the gas introduced into the CZ furnace. Yes. By controlling the relative position of the lower surface of the heat shield and the melt level (that is, the distance between them), the thermal history and impurity concentration (oxygen concentration, etc.) in the pulled single crystal can be made constant. . Therefore, conventionally, various melt level measurement methods have been proposed.

  In Patent Document 1 below, the melt level is measured based on the principle of triangulation by utilizing the shape of the liquid surface that is constantly generated by the fluctuation of the melt surface and making it function as a kind of reflector. A method of performing is disclosed. Hereinafter, this measurement method is also referred to as “direct reflection method”.

  FIG. 10 is a diagram for explaining the locus of laser light by the conventional direct reflection method. 10A is a schematic diagram of the laser beam trajectory viewed from the side surface (XY plane), and FIG. 10B is a schematic diagram of the laser beam trajectory viewed from the front surface (XZ plane). is there. As shown in FIG. 10A, the laser light is guided through the rotating mirror 9 and the prism 11, but in FIG. 10B, the locus of the laser light in the Y-axis direction penetrates the paper surface. The rotating mirror 9 and the prism 11 are not shown because they extend in the direction. Also, illustration of parts that are not essential for triangulation is omitted.

  As shown in FIGS. 10A and 10B, in the single crystal pulling apparatus, a silicon raw material melt (silicon melt) 3 is placed in a crucible 2 provided in the CZ furnace 1. The silicon single crystal 4 is pulled up and grown while rotating upward. A heat shield 5 is disposed outside the silicon single crystal 4.

  In this single crystal pulling apparatus, in order to measure the position (melt level) of the liquid surface 7 of the melt 3, a distance measuring unit 8 based on the principle of triangulation is employed.

  As shown in FIG. 10B, a laser light source 12 that projects laser light and a light receiver 13 that receives reflected light reflected are provided inside the distance measuring unit 8. The light receiver 13 is provided with a condenser lens 13a for condensing incident laser light and a CCD sensor 13b 'for detecting the laser light condensed by the condenser lens 13a.

The laser beam emitted from the distance measuring unit 8 is reflected by the rotating mirror 9, passes through the incident window 10, passes through the prism 11 installed inside the CZ furnace 1, and then reaches the liquid level 7 of the melt 3. Projected on.
Here, the rotating mirror 9 is rotated in the left-right direction (the direction of the arrow S1 in FIG. 10B), and the projection position of the laser beam on the liquid surface 7 of the melt 3 is changed in the radial direction of the crucible 2 (FIG. 10B). The reflected light reflected by the liquid surface 7 of the melt 3 is received by the light receiver 13 at a predetermined frequency via the prism 11, the incident window 10 and the rotating mirror 9. ing. Thus, in the direct reflection method, the laser light emitted from the laser light source is directly projected onto the liquid surface 7 of the melt 3, and the reflected light reflected by the liquid surface 7 of the melt 3 is directly received by the light receiver 13. Is done.

  As shown in FIG. 10 (b), when the melt level of the liquid surface 7 of the melt 3 is at the position A1, the laser beam reflected by the liquid surface 7 of the melt 3 is measured at the coordinate X1 of the CCD sensor 13b ′. Is detected. That is, the measurement coordinate X1 of the CCD sensor 13b 'corresponds to the melt level A1. Similarly, when the melt level is A2, the laser beam reflected by the liquid surface 7 of the melt 3 is detected at the measurement coordinate X2 of the CCD sensor 13b '. That is, the measurement coordinate X2 of the CCD sensor 13b 'corresponds to the melt level A2. In this way, the melt level can be measured from the measurement coordinates detected by the CCD sensor 13b 'based on the principle of triangulation.

  In FIG. 10B, the incident angle and the reflection angle (both angles θ1) of the laser beam to the liquid surface 7 of the melt 3 are shown to be large, but in reality both angles θ1 are several degrees. It is a small angle. The same applies to other drawings.

JP 2000-264777 A

In the melt level measurement method described in Patent Document 1, a one-dimensional optical sensor or a two-dimensional optical sensor is used as the optical sensor in the light receiver.
The one-dimensional photosensor (line sensor) has an advantage that a high-resolution (high pixel count) sensor can be realized at a relatively low cost. On the other hand, there is a disadvantage that the detectable range of light is linear (line shape) and narrow, and the alignment of the light receiving position is complicated.

On the other hand, according to the two-dimensional optical sensor (area sensor), the light detection range is wide (planar), and the light receiving position can be easily or substantially not aligned. There is. On the other hand, it is susceptible to noise such as ghost light and camera pixel omission (dot drop), which has the disadvantage that measurement accuracy tends to decrease.
When using a photoreceiver with a two-dimensional photosensor, if the reduction in measurement accuracy caused by the two-dimensional photosensor, such as ghost light or missing pixels, can be suppressed, the advantage of easy or unnecessary positioning of the photodetection position can be obtained. Can be desirable.

  The present invention has been made in view of the above problems, and uses a position measurement device including a photoreceiver having a two-dimensional photosensor, and decreases measurement accuracy caused by the two-dimensional photosensor such as ghost light or missing pixels. It is an object of the present invention to provide a position measuring method and a position measuring apparatus capable of suppressing the above-described problem and obtaining the advantage that the alignment of the light receiving position is easy or unnecessary.

(1) The position measuring method of the present invention uses a position measuring device including a light source and a light receiver having a two-dimensional photosensor, and measures the location of a Czochralski furnace in a single crystal pulling device for emitting light emitted from the light source. The reflected light reflected at the measurement location is received by the two-dimensional light sensor of the light receiver, and the principle of triangulation is used based on the brightness of the reflected light received by the two-dimensional light sensor. A position measuring method for measuring the position of the measurement location, wherein a direction in which the reflected light represents the position of the measurement location in the two-dimensional optical sensor is referred to as a first direction, and a direction orthogonal to the first direction In the case of the second direction, based on the second direction centroid calculating step of calculating the second direction centroid which is the centroid of the second waveform indicating the luminance of the reflected light along the second direction, and the second direction centroid. A first direction center position calculating step for calculating a first direction center position which is the center of the first waveform indicating the luminance of the reflected light along the first direction, and the measurement based on the first direction center position. A measurement location calculation step for calculating the location of the location.

(2) In the first direction center position calculating step, when calculating the first direction center position based on the second direction center of gravity, the second direction including the second direction center of gravity in the second waveform. It is preferable to use a region in a predetermined range of directions.

(3) In the second direction centroid calculating step, it is preferable that the second direction centroid is calculated after removing a portion including luminance detected with a magnitude equal to or smaller than a predetermined threshold for the second waveform. .

(4) Moreover, the said measurement location is the liquid level of the melt accommodated in the crucible provided in the inside of the said Czochralski furnace, and / or the heat shield provided in the inside of the said Czochralski furnace. It is preferable.

(5) The position measuring device of the present invention includes a light source and a light receiver having a two-dimensional photosensor, and projects the emitted light emitted from the light source to a measurement location related to the Czochralski furnace in the single crystal pulling device, The reflected light reflected at the measurement location is received by the two-dimensional photosensor of the receiver, and the principle of triangulation is used based on the brightness of the reflected light received by the two-dimensional photosensor. In the position measuring device for measuring a position, in the two-dimensional photosensor, a direction in which the reflected light indicates the position of the measurement location is referred to as a first direction, and a direction orthogonal to the first direction is referred to as a second direction. In addition, based on the second direction center of gravity, second direction center of gravity calculation means for calculating a second direction center of gravity of the second waveform indicating the brightness of the reflected light along the second direction, the first direction based on the first direction, Along the direction A first direction center position calculating means for calculating a first direction center position that is the center of the first waveform indicating the brightness of the reflected light, and a measurement for calculating the position of the measurement location based on the first direction center position. And a location calculating means.

  According to the position measuring method and the position measuring apparatus of the present invention, a position measuring apparatus including a light receiver having a two-dimensional photosensor is used to suppress a decrease in measurement accuracy caused by the two-dimensional photosensor, such as ghost light or missing pixels. And the advantage that the alignment of the light receiving position is easy or unnecessary can be obtained.

Hereinafter, a first embodiment of a position measuring method of the present invention and a first embodiment of a position measuring apparatus of the present invention will be described with reference to the drawings.
1 and 2 are diagrams for explaining the locus of laser light in the first embodiment of the position measuring method of the present invention and the first embodiment of the position measuring apparatus of the present invention. FIG. 1A is a schematic diagram of the laser beam trajectory viewed from the side (XY plane), and FIG. 1B is a schematic diagram of the laser beam trajectory viewed from the front (XZ plane). is there. As shown in FIG. 1A, the laser beam is guided through the rotating mirror 9 and the prism 11, but in FIG. 1B, the locus of the laser beam in the Y-axis direction penetrates the paper surface. The rotating mirror 9 and the prism 11 are not shown because they extend in the direction. Also, illustration of parts that are not essential for triangulation is omitted. FIG. 2 is a schematic view of the locus of laser light as viewed from the upper surface (YZ plane).

  The position measuring method according to the first embodiment is a method using the position measuring apparatus according to the first embodiment. As shown in FIGS. 1 and 2, the crucible provided inside the CZ furnace 1 in the single crystal pulling apparatus. This is a method of measuring the position (melt level) of the liquid surface 7 of the melt 3 accommodated in the (crucible). First, the position measuring apparatus according to the first embodiment will be described.

  As shown in FIGS. 1 and 2, the position measurement device of the first embodiment is provided in a single crystal pulling device, and mainly includes a distance measurement unit 8, a rotating mirror 9, a prism 11, and the like. The distance measuring unit 8 includes a laser light source (light source) 12 that projects laser light onto the liquid surface 7 of the melt 3 and a light receiver 13 that receives the laser light reflected from the liquid surface 7 of the melt 3. Yes. The light receiver 13 includes a condensing lens 13a that condenses the laser light incident therein, and a CMOS sensor 13b as a two-dimensional optical sensor that detects the luminance of the condensed laser light.

  The position measurement apparatus according to the first embodiment uses the principle of triangulation based on the brightness of the reflected light received by the CMOS sensor 13b, and directly performs the melt level (the liquid level 7 of the melt 3). ). That is, in the position measurement apparatus of the first embodiment, the laser light emitted from the laser light source 12 is projected onto the liquid surface 7 of the melt 3 via the rotating mirror 9 and the prism 11, and the liquid surface 7 of the melt 3 is projected. The reflected light reflected by is received by the CMOS sensor 13 b in the light receiver 13.

  As shown in FIG. 1, the single crystal pulling apparatus includes a CZ furnace 1 and a crucible 2 provided inside the CZ furnace 1, and a silicon raw material melt (silicon melt) 3 is accommodated in the crucible 2. Has been. In the single crystal pulling apparatus, the silicon single crystal 4 is pulled and grown while rotating upward. A heat shield 5 is disposed outside the silicon single crystal 4.

  In the position measuring apparatus and the single crystal pulling apparatus having the above-described configuration, as shown in FIGS. 1 and 2, the laser light emitted from the laser light source 12 of the distance measuring unit 8 is reflected by the rotating mirror 9 and is incident. The light passes through the window 10 and is directly projected onto the liquid surface 7 of the melt 3 via the prism 11 installed inside the CZ furnace 1. The reflected light reflected by the liquid surface 7 of the melt 3 is guided through the prism 11, the incident window 10, and the rotating mirror 9 through the path opposite to that at the time of projection, and is received by the CMOS sensor 13 b of the light receiver 13. The

  The rotating mirror 9 is rotated in the left-right direction (in the direction of arrow S1 in FIG. 1B), and the projection position of the laser light on the liquid surface 7 of the melt 3 is set in the radial direction of the crucible 3 (in the arrow S2 in FIG. 1B). The reflected light reflected by the liquid surface 7 of the melt 3 is received by the light receiver 13 at a predetermined frequency via the prism 11, the incident window 10, and the rotating mirror 9. Thus, the laser light emitted from the laser light source is directly projected on the liquid surface 7 of the melt 3, and the reflected light reflected by the liquid surface 7 of the melt 3 is directly received by the light receiver 13.

  As shown in FIG. 1B, when the melt level of the liquid surface 7 of the melt 3 is at the position A1, the laser light reflected by the liquid surface 7 of the melt 3 is emitted from the CMOS sensor 13b of the light receiver 13. It is detected at the measurement coordinate X1. That is, the measurement coordinate X1 of the CMOS sensor 13b corresponds to the melt level A1. Similarly, when the melt level is A2, the laser beam reflected by the liquid surface 7 of the melt 3 is detected at the measurement coordinate X2 of the CMOS sensor 13b. That is, the measurement coordinate X2 of the CMOS sensor 13b corresponds to the melt level A2. In this way, based on the principle of triangulation, the melt level can be measured from the measurement coordinates detected by the CMOS sensor 13b.

  In the XZ plane shown in FIG. 1B, the laser light projected from the laser light source 12 onto the liquid surface 7 of the melt 3 at the incident angle θ1 is reflected at the liquid surface 7 at the reflection angle θ1. In addition, in the XY plane shown in FIG. 1A, the laser beam reflected by the liquid surface 7 of the melt 3 advances toward the CMOS sensor 13b while maintaining the angle θ1 in the XZ plane, and the measurement coordinates. X1 is detected. The melt level A1 corresponds to the measurement coordinate X1 of the CMOS sensor 13b.

  As described above, as shown in FIG. 1B, by performing triangulation on the XZ plane, the height position in the X-axis direction, that is, the position of the liquid surface 7 of the melt 3 (melt level). Can be measured.

  Next, the CMOS sensor 13b as a two-dimensional photosensor will be described. FIG. 3 is a perspective view schematically showing a state in which reflected light is received by the CMOS sensor 13b. FIG. 4 is a diagram schematically showing the light receiving region ER, the first waveform J1, and the second waveform J2 of the CMOS sensor 13b.

  As shown in FIGS. 3 and 4, the CMOS sensor 13b receives the reflected light collected by the condenser lens 13a. In the CMOS sensor 13b, which is a two-dimensional photosensor, a direction indicating the position of the measurement location 7a is referred to as a first direction D1, and a direction orthogonal to the first direction D1 is referred to as a second direction D2. The light receiving region ER of the CMOS sensor 13b has an x axis extending in the first direction D1 and a y axis extending in the second direction.

  The imaging spot R1 of the reflected light received by the CMOS sensor 13b extends in the first direction D1 (x-axis direction). The reason is as follows. The imaging spot R1 of the reflected light is substantially circular with respect to the cross-sectional shape in the direction intersecting with the optical axis of the laser light (axis extending in the traveling direction), but the light receiving surface of the light receiving region ER of the CMOS sensor 13b is the optical axis. It is not orthogonal to the optical axis and is inclined with respect to the plane orthogonal to the optical axis (for example, 15 to 20 degrees). Therefore, the imaging spot R1 extends in the first direction D1 (x-axis direction) on the light receiving surface of the CMOS sensor 13b.

  The reason why the light receiving surface of the CMOS sensor 13b is inclined with respect to the plane orthogonal to the optical axis is as follows. When a fixed focus lens (a lens that does not have an autofocus function) is used as the condenser lens 13a, when the position (melt level) of the measurement location 7a changes, the change does not depend on the location of the measurement location 7a. This is because the focus of the imaging spot corresponding to the amount can be adjusted along the first direction D1.

  The light receiver 13 can include a dark filter (not shown) that cuts light having a predetermined luminance or less. The extinction filter is disposed on the front side (measurement location 7a side) of the condenser lens 13a. According to the neutral density filter, saturation of the received light luminance of the reflected light in the CMOS sensor 13b is suppressed. Moreover, it is possible to suppress the diffusion laser light from being imaged by the CMOS sensor 13b by dimming the diffuse reflection light of the laser light emitted from the laser light source 12 by the extinction filter.

  In FIG. 4, the imaging spot R1 of the reflected light of the laser beam is received in the light receiving region ER. The first waveform J1 is a waveform indicating the luminance of reflected light along the first direction D1 (x-axis direction). The second waveform J2 is a waveform indicating the brightness of the reflected light along the second direction D2 (y-axis direction). Ideally, the center of the imaging spot R1 of the reflected light is located at the center of the first waveform J1 and the center of gravity of the second waveform J2.

  In the light receiving region ER, noise R2 exists separately from the imaging spot R1. The noise R2 lowers the measurement accuracy when calculating the second direction center of gravity in a second direction center of gravity calculation step ST2, which will be described later, and calculating the first direction center position in the first direction center position calculation step ST3. Therefore, it is preferable to remove the noise R2 as much as possible.

Next, a configuration related to calculation of various values in the position measurement apparatus of the first embodiment will be described with reference to FIG. FIG. 5 is a functional block diagram showing a configuration relating to calculation of various values in the first embodiment of the position measuring apparatus of the present invention.
As shown in FIG. 5, the position measurement device according to the first embodiment includes a calculation unit 14. The calculation unit 14 controls the projection of the laser light from the laser light source 12 and calculates various values based on the luminance of the laser light received by the light receiver 13 (CMOS sensor 13b).
The calculation unit 14 functions as the second direction center of gravity calculation unit 14a, the first direction center position calculation unit 14b, and the measurement location calculation unit 14c.

The second direction centroid calculating means 14a calculates the second direction centroid which is the centroid of the second waveform J2 indicating the luminance of the reflected light along the second direction D2 (y-axis direction).
The first direction center position calculating means 14b calculates the first direction center position that is the center of the first waveform J1 indicating the luminance of the reflected light along the first direction D1 (x-axis direction) based on the second direction center of gravity. To do.
The measurement location calculation means 14c calculates the position (melt level) of the measurement location 7a based on the center position in the first direction.

Next, a position measuring method according to the first embodiment using the position measuring apparatus according to the first embodiment will be described with reference to FIG. FIG. 6 is a flowchart showing a first embodiment of the position measuring method of the present invention.
As shown in FIG. 6, the position measuring method of the first embodiment includes the following laser light receiving step ST1, second direction center of gravity calculating step ST2, first direction center position calculating step ST3, and measurement point calculating step ST4.

(ST1) Laser Light Receiving Step Laser light emitted from the laser light source 12 is projected onto the liquid surface 7 of the melt 3 via the rotating mirror 9 and the prism 11, and the reflected light reflected by the liquid surface 7 of the melt 3 is reflected. Light is received by the CMOS sensor 13 b in the light receiver 13.
Here, as shown in FIG. 4, it is assumed that the imaging spot R1 of the reflected light of the laser beam is received and the noise R2 is present in the light receiving region ER of the CMOS sensor 13b.

(ST2) Second Direction Center of Gravity Calculation Step The second waveform J2 indicating the luminance of the reflected light along the second direction D2 in the reflected light received by the CMOS sensor 13b in the laser light receiving step ST1 is the second center that is the center of gravity. Calculate the centroid of the direction.
In the present embodiment, the second direction center of gravity is calculated after removing the portion including the luminance detected with a magnitude equal to or smaller than a predetermined threshold value for the second waveform J2, that is, the noise R2.

  Note that the center of gravity in the present invention is the center position of the measurement location with the luminance value of the pixel as a weight. A specific method of calculating the center of gravity is represented by an arbitrary point P (x, y) when the imaging spot R1 is in the XY coordinate system. Therefore, the luminance distribution of the imaging spot R1 is represented by m (x, y). Then, the center-of-gravity position C (cx, cy) can be solved by the following integral expressions (1) and (2).

  The noise R2 forms a peak K22 different from the peak K21 corresponding to the imaging spot R1 in the second waveform J2. However, in general, the peak K22 corresponding to the noise R2 is clearly smaller in luminance than the peak K21 corresponding to the imaging spot R1. Therefore, a threshold that can appropriately distinguish between the peak K21 corresponding to the imaging spot R1 and the peak K22 corresponding to the noise R2 is set, and both peaks K21 and K22 are distinguished based on this threshold.

In addition, when there is a peak in the second waveform J2, any peak may not be the peak K21 corresponding to the imaging spot R1.
Therefore, a threshold BL22 for distinguishing the peak K21 corresponding to the imaging spot R1 and the peak K22 corresponding to the noise R2 and a threshold BL21 for confirming that the peak K21 corresponds to the imaging spot R1 are set. To do.

  The threshold value BL22 for distinguishing between the peak K21 corresponding to the imaging spot R1 and the peak K22 corresponding to the noise R2 is, for example, 50 to 70% with respect to the maximum value of luminance that can be measured by the CMOS sensor 13b. The threshold value BL21 for confirming that the peak K21 corresponds to the imaging spot R1 is, for example, 80 to 100% with respect to the maximum luminance value that can be measured by the CMOS sensor 13b.

Note that the peak K22 corresponding to the noise R2 is determined based on the size of the spot image area in the light receiving region ER of the CMOS sensor 13b in addition to the method of simply determining the luminance level as described above. it can. For example, when the area of the spot image in the light receiving region ER of the CMOS sensor 13b is smaller than a predetermined threshold, it can be determined that the spot image is the peak K22 corresponding to the noise R2.
In the second direction centroid calculation step ST2, by performing one or both of the peak determination and the area determination, it is possible to determine and select noise and ghost light generated in the second direction D2.

  A specific example of removing ghost light will be described. FIG. 7A is a graph showing a measurement example of the ghost light R3. FIG. 7B is a schematic diagram showing an outline of a method for measuring a position related to a beam. FIG. 7C is a schematic diagram showing the inside of the region above the threshold BL22. As shown in FIG. 7, in order to remove the ghost light R3, the area of the beam lump in the WOI area of the area camera is determined, and the second direction D2 (y-axis direction) targeting a predetermined luminance threshold or more ) Is calculated by the following procedures (1) to (7). Here, as the brightness threshold BL22, 50 to 70% of the difference between the maximum value and the minimum value of brightness is used.

(1) Since the position of the imaging spot (beam for extracting the center of gravity) R1 is known in advance, a range (WOI region) for performing the image processing is designated.
(2) In the WOI region, binarization of luminance is performed with a region having a threshold BL22 or more as a portion with luminance (value: 1) and a region below it as a portion without luminance (value: 0).
(3) A search is performed for a binarized portion having a luminance.
(4) When a plurality of masses of the target beam are detected, the area of the mass is determined (for example, when the imaging spot R1 and the ghost light R3 are detected).
(5) A region where the sum of luminance values in a rectangle circumscribing the block is maximized is determined to be a region where the imaging spot R1 exists.
(6) Within the region, the center of gravity is calculated using the integration equations (1) and (2) at a luminance value equal to or higher than the threshold BL22.
(7) The center of gravity is determined to be the center of gravity in the second direction D2 (y-axis direction).

(ST3) First direction center position calculating step First waveform J1 indicating the brightness of reflected light along the first direction D1 (x-axis direction) based on the second direction center of gravity calculated in the second direction center of gravity calculating step ST2. Is calculated, the center position in the first direction is calculated.

  A specific calculation method of the first direction center position is as follows. First, predetermined threshold values (threshold value BL11 and threshold value BL12) are set to about 5 to 30 in the maximum luminance 255 in the first waveform J1 shown in FIG. Then, it is preferable to calculate the center position in the first direction after removing in advance the waveform component including the luminance detected with a size smaller than that, that is, noise and ghost light.

  Further, since the first waveform J1 has a Gaussian distribution of received light intensity as shown in FIG. 8, for example, the first waveform J1 is obtained by a Gaussian fitting method that performs matching by a normalized correlation function using a Gaussian function as a model function. The center position of J1 is accurately obtained, and the center position of the imaging spot in the first direction D1 corresponding to the center of gravity in the second direction is determined as the first direction center position (pixel).

  Note that a threshold value can be provided for the correlation coefficient when the Gaussian fitting method is performed. For example, in the case where the measurement location is the level of the melt contained in a crucible provided inside the CZ furnace, the threshold value of the correlation coefficient is in the range of 70 to 100%. When the measurement location is a heat shield provided inside the CZ furnace, the correlation coefficient threshold is in the range of 60-80%. Since noise and ghost light are originally weakly correlated with a normalized correlation coefficient using a Gaussian function as a model function, noise generated in the first direction by using the first waveform J1 that is equal to or greater than the threshold value for the calculation of the center position. And ghost light can be removed.

  If the first direction center position is simply calculated based on the center of gravity in the first direction without performing the Gaussian fitting method, the first waveform J1 is unlikely to be a normal distribution curve. In particular, when the measurement location is a heat shield provided inside the CZ furnace, the surface of the heat shield is not in a smooth specular state, so that the reflected light becomes diffuse light with a mottled brightness. As a result, the first waveform J1 does not become a normal distribution curve as shown in FIG. For this reason, an error tends to occur at the center position in the first direction. Therefore, this problem is solved by performing the Gaussian fitting method.

In the present embodiment, when the first direction center position is calculated based on the second direction center of gravity, a region in a predetermined range in the second direction D2 including the second direction center of gravity in the second waveform J2 is used. That is, projection (weighted average, for example, for example, a width of ± 10 pixels centered on a pixel located in the second direction center of gravity) in the second range including the second direction center of gravity in the second waveform J2 A process of dividing the luminance sum of 21 pixels by 21) is performed, a first waveform J1 corresponding to this region is calculated, and a Gaussian fitting method is performed to accurately obtain the center position. Then, the center position of the imaging spot in the first direction D1 corresponding to the center of gravity in the second direction is determined as the first direction center position (pixel).
By performing the projection (weighted average), noise other than the first waveform J1 and small light that is ghost light are averaged and necessarily reduced (for example, 1/21 luminance). Thereby, noise and ghost light generated in the first direction can be removed.

  The second direction center of gravity calculation step ST2 and the first direction center position calculation step ST3 are mainly performed to remove the influence of ghost light received by the CMOS sensor 13b. The ghost light is generated mainly due to multiple reflection in the CZ furnace 1 of the single crystal pulling apparatus. As a cause of the multiple reflection, there is a reflection in the heat shield 5 and the gate in the CZ furnace 1.

(ST4) Measurement location calculation step The position of the measurement location 7a is calculated based on the first direction center location calculated in the first direction center location calculation step ST3. That is, the actual distance (position) is obtained by substituting the calculated position value (pixel) of the center in the first direction into a function that converts the value to the distance to the measurement location 7a expressed by, for example, a quartic equation. be able to.

  As described above, according to the position measurement method of the first embodiment and the position measurement apparatus of the first embodiment, it is possible to suppress a decrease in measurement accuracy caused by a two-dimensional photosensor such as noise, ghost light, and pixel omission. The advantage that the alignment of the light receiving position is easy or unnecessary can be obtained. Therefore, the position of the liquid surface 7 of the melt 3 that affects the quality of the single crystal by the CZ method, the position of the in-furnace member such as the heat shield 5 (described later), etc. are measured with high accuracy and the position is maintained. As a result, variations in the quality of single crystals can be reduced, and high-quality single crystals can be stably produced.

Although the first embodiment and the first embodiment of the present invention have been described above, the present invention is not limited to the first embodiment and the first embodiment described above.
For example, in the above-described embodiment and embodiment, the measurement point 7a is the liquid level 7 of the melt 3 accommodated in the crucible 2 provided inside the CZ furnace 1, but is not limited thereto, and the CZ A heat shield 5 provided inside the furnace 1 may be used. Alternatively, both the liquid surface 7 of the melt 3 and the heat shield 5 can be measured. In this case, the distance (interval) between the liquid surface 7 of the melt 3 and the heat shield 5 (particularly, the bottom surface 6) is measured. Can be measured.

The two-dimensional photosensor is not limited to the CMOS sensor 13b, and for example, an area type CCD or PSD can be used.
In the embodiment and the embodiment, a so-called direct measurement method is used. However, the measurement method is not limited to this, and the measurement method described in WO01 / 083859 (reflection on the bottom surface 6 of the heat shield 5 is used). ) Or a measurement method described in Japanese Patent Application Laid-Open No. 2007-223879 (utilization of reflection on a side surface of the heat shield 5 or the like) can be used.

Red laser light, purple laser light, blue laser light, and green laser light can also be used as the laser light.
In place of the laser light source, a light source such as xenon, mercury, or halogen, or a single wavelength light source such as sodium wire may be used.

(A) is the schematic diagram which looked at the locus | trajectory of the laser beam from the side surface (XY plane), (b) is the schematic diagram which looked at the locus | trajectory of laser beam from the front (XZ surface). It is the schematic diagram which looked at the locus of the laser beam from the upper surface (YZ plane). It is a perspective view which shows typically the state by which reflected light is received by the CMOS sensor 13b. It is a figure which shows typically the light reception area | region ER of the CMOS sensor 13b, the 1st waveform J1, and the 2nd waveform J2. It is a functional block diagram which shows the structure which concerns on calculation of the various values in 1st Embodiment of the position measuring apparatus of this invention. It is a flowchart which shows the 1st embodiment of the position measuring method of this invention. It is a figure explaining the specific example which removes ghost light. It is a figure which shows distribution of the light-receiving luminance about the image imaged along a 1st direction. It is a figure which shows distribution of the light reception brightness | luminance of the 1st direction in which the Gaussian fitting method is more effective than the brightness | luminance gravity center method in the case of not performing matching. (A) is the schematic diagram which looked at the locus | trajectory of the laser beam from the side surface (XY plane), (b) is the schematic diagram which looked at the locus | trajectory of laser beam from the front (XZ surface).

Explanation of symbols

1 CZ furnace (Czochralski furnace)
2 Crucible 3 Silicon melt (melt)
4 Silicon single crystal (single crystal)
DESCRIPTION OF SYMBOLS 5 Heat shield 6 Bottom surface of heat shield 7 Liquid surface 7a Measurement location 8 Distance measurement unit 9 Rotating mirror 10 Entrance window 11 Prism 12 Laser light source (light source)
13 Photoreceiver 13a Condensing lens 13b CMOS sensor (two-dimensional optical sensor)
13b 'CCD sensor (one-dimensional optical sensor)
14a Second direction center of gravity calculation means 14b First direction center position calculation means 14c Measurement location calculation means D1 First direction D2 Second direction J2 Second waveform J1 First waveform ST2 Second direction center of gravity calculation step ST3 First direction center position calculation Process ST4 Measurement location calculation process

Claims (5)

Using a position measuring device including a light source and a light receiver having a two-dimensional optical sensor, the emitted light emitted from the light source is projected to a measurement location related to the Czochralski furnace in the single crystal pulling device, and reflected at the measurement location. Position measurement in which light is received by the two-dimensional light sensor of the light receiver and the position of the measurement point is measured using the principle of triangulation based on the luminance of the reflected light received by the two-dimensional light sensor A method,
In the two-dimensional photosensor, when the reflected light indicates the position of the measurement location is referred to as a first direction, and the direction orthogonal to the first direction is referred to as a second direction,
A second direction centroid calculating step of calculating a second direction centroid which is a centroid of the second waveform indicating the luminance of the reflected light along the second direction;
A first direction center position calculating step of calculating a first direction center position, which is the center of the first waveform indicating the luminance of the reflected light along the first direction, based on the second direction center of gravity;
And a measurement location calculation step of calculating the location of the measurement location based on the center position in the first direction.   In the first direction center position calculating step, when calculating the first direction center position based on the second direction center of gravity, a predetermined range in the second direction including the second direction center of gravity in the second waveform The position measuring method according to claim 1, wherein the region is used.   2. The second direction centroid is calculated after removing a portion including luminance detected with a magnitude of a predetermined threshold value or less in the second waveform in the second direction centroid calculating step. Or the position measuring method of 2.   The measurement location is a liquid level of a melt contained in a crucible provided inside the Czochralski furnace and / or a heat shield provided inside the Czochralski furnace. The position measuring method according to claim 1. A light source and a light receiver having a two-dimensional optical sensor, and projecting the emitted light emitted from the light source to a measurement location related to a Czochralski furnace in a single crystal pulling apparatus, and reflecting the reflected light reflected at the measurement location A position measurement device that measures the position of the measurement location using the principle of triangulation based on the brightness of the reflected light received by the two-dimensional photosensor,
In the two-dimensional photosensor, when the reflected light indicates the position of the measurement location is referred to as a first direction, and the direction orthogonal to the first direction is referred to as a second direction,
Second direction gravity center calculating means for calculating a second direction gravity center that is a gravity center of the second waveform indicating the luminance of the reflected light along the second direction;
First direction center position calculating means for calculating a first direction center position, which is the center of the first waveform indicating the luminance of the reflected light along the first direction, based on the second direction center of gravity;
And a measurement location calculation means for calculating the location of the measurement location based on the center position in the first direction.

Images