TWI593836B - A method of controlling a liquid level of a melt flow - Google Patents

Description

Method for controlling the position of molten soup

The invention relates to the casting of a crystal rod; in particular to a method for controlling the position of a molten liquid surface.

The conventional crystal growth furnace comprises a crucible and a plurality of heaters for containing raw materials to be melted, and the heaters are disposed around the crucible for heating the crucible to melt the raw materials in the crucible into a liquid state Melt soup. When casting the ingot, the seed crystal is immersed in the melt, and the seed crystal is pulled up to perform seeding, and finally the crystal ingot is formed. However, in the process of casting the ingot, the melting of the crucible will decrease as the length of the ingot grows, that is, the position of the molten liquid is continuously decreased.

After the molten liquid level drops, the thermal field of the liquid surface will change and the temperature of the liquid surface will change. The change of the liquid surface temperature will result in different quality of the crystal rod from top to bottom. In particular, if the body of the ingot is of different quality from top to bottom, the wafer quality will be cut by the same ingot. Therefore, it is necessary to control the height of the crucible while casting the ingot, and to maintain the molten liquid level in a stable position as much as possible.

It is known to monitor the position of the molten liquid surface, including the visual observation, the laser light ranging, the measurement of the radius of the crystal rod or the diameter to reverse the change of the liquid level position. However, the accuracy of the foregoing method is insufficient. The position of the liquid surface is accurately known, and therefore, only the position of the liquid level of the melt can be roughly controlled.

In view of the above, an object of the present invention is to provide a method for controlling the position of a molten liquid surface, which can accurately control the position of the molten liquid surface.

In order to achieve the above object, the present invention provides a method for controlling the position of a molten liquid surface, which is applied to a crystal growth furnace, wherein the crystal growth furnace includes a crucible and a heat shield disposed above the crucible. In the molten soup, the heat shield has an opening corresponding to the inside of the casing; the control method comprises the following steps: A. providing a camera module, the camera module is obtained from the upper side of the opening of the heat shield An image of the liquid surface of the molten soup; B. obtaining an image captured by the camera module, and determining an area of at least one shaded area included in the image according to the acquired image; C, according to the area of the shadow area The position of the crucible in the vertical direction is controlled such that the liquid level of the molten soup is maintained at a predetermined distance from the bottom surface of the heat shield.

The present invention further provides a method for controlling the position of a molten liquid surface, comprising the following steps: A. providing a photographic module, the photographic module picking up the molten broth from the opening of the opening of the heat absorbing cover The image of the face; B, in the process of casting the body of the ingot, continuously obtaining the image captured by the camera module, and corresponding to the image obtained, corresponding to the area of at least one shaded area included in the image C. Control the position of the 坩埚 in the vertical direction according to the area of the shadow area in the image, so that the area of the shadow area is maintained at a predetermined area.

The effect of the present invention is that by judging the area of the shaded area in the image, the position of the molten liquid level in the sputum can be accurately determined, so that the movement of the sputum can be accurately controlled so that the liquid surface is in a stable thermal field.

〔this invention〕

100‧‧‧Crystal furnace

10‧‧‧ furnace body

102‧‧‧ Observatory

20‧‧‧坩埚

30‧‧‧heater

40‧‧‧heat shield

42‧‧‧ channel

44‧‧‧ bottom

442‧‧‧ openings

50‧‧‧First drive

52‧‧‧Second drive

54‧‧‧ support

60‧‧‧ molten soup

602‧‧‧ liquid level

70‧‧‧ pull rod

72‧‧‧ seed crystal

74‧‧‧Ingot

80‧‧‧Photography module

82‧‧‧Control device

L1, L2‧‧‧ distance

S1, S2, S3‧‧‧ shadow area

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a crystal growth furnace to which a method for controlling the position of a molten liquid surface according to a first preferred embodiment of the present invention is applied.

2 is a flow chart showing a method for controlling the position of a molten liquid surface according to a first preferred embodiment of the present invention.

3 and 4 are schematic views showing the relationship between the distance between the liquid surface and the bottom surface of the heat shield and the shaded area in the image.

Figure 5 is a partial image captured by the camera module during the process of casting the body of the ingot.

Figure 6 is a flow chart showing a method of controlling the position of a molten liquid in a second preferred embodiment of the present invention.

In order to explain the present invention more clearly, a preferred embodiment will be described in detail with reference to the drawings. Referring to FIG. 1 , a crystal growth furnace 100 is applied to a method for controlling the position of a molten liquid surface according to a first preferred embodiment of the present invention. The crystal growth furnace 100 includes a furnace body 10 , a crucible 20 , and a plurality of The heater 30, a heat shield 40, a first driving device 50, and a second driving device 52.

The upper right half of the furnace body 10 has an observation port 102 communicating with the inside of the furnace body 10. The crucible 20 is disposed on a support seat 54 in the furnace body 10 for placing a raw material to be melted (for example, a solid crucible material). The heaters 30 are disposed on the periphery of the crucible 20 for heating the crucible 20 to melt the raw material inside the crucible 20 into the melt 60. The heat shield 40 is disposed above the crucible 20 to prevent part of the thermal energy from escaping from the liquid surface 602 of the melt 60. The heat shield 40 has a passage 42 which is a wide and narrow tapered shape. And the channel 42 has a circular opening 442 corresponding to the bottom surface 44 of the heat shield 40 corresponding to the inside of the crucible 20. The first driving device 50 is disposed above the furnace body 10, and the first driving device 50 is used to drive a pull rod 70 rotation and up and down movement, the bottom end of the crystal pulling rod 70 is provided with a seed crystal 72, the pull rod 70 is inserted into the crucible 20 from the passage 42 of the heat shield 40, so that the seed crystal 72 contacts the melt 60 is used for seeding to form the ingot 74. The second driving device 52 is configured to drive the support base 54 to move up and down, thereby driving the crucible 20 to be displaced in the vertical direction.

The following steps shown in FIG. 2 can be performed by using the crystal growth furnace 100 described above: First, a photographic module 80 and a control device 82 are provided, and the photographic module 80 is mounted on the furnace body 10 and located at Corresponding to the observing port 102, the camera module 80 is photographed obliquely from the upper right to the lower left direction. The viewing angle of the photographic module 80 encompasses the lower half of the channel 42 of the heat shield 40 and the level 602 of the melt 60 below the channel 42. In other words, the camera module 80 captures an image of the liquid level 602 of the melt 60 in the crucible 20 from obliquely above the opening 442 of the heat shield 40. The bottom surface 44 of the heat shield 40 will be reflected on the liquid level 602 of the melt 60 to form a shadow. The control device 82 is electrically connected to the camera module 80 and the second driving device 52 for receiving the image captured by the camera module 80, performing subsequent analysis and calculation, and making the second driver Device 52 drives the cassette 20 to move.

Please refer to FIG. 3 and FIG. 4 to illustrate the relationship between the distance between the liquid surface 602 of the molten stone 60 and the bottom surface 44 of the heat shield 40 and the image captured by the camera module 80. For ease of understanding, FIG. 3 and FIG. 4 The middle portion is described in the stage before the seed crystal 72 is immersed in the melt 60, and therefore, the amorphous rod 74 is present in the drawing. Since the photographic module 80 is photographed from the upper right to the lower left direction, and the distance L1 between the bottom surface 44 of the heat shield 40 and the liquid surface 602 in FIG. 3 is relatively close, the bottom surface 44 of the heat shield 40 is reflected in the melt. The shadow of the 60 liquid surface 602 is largely covered by the heat shield 40, and therefore, the shaded area S1 on the liquid surface 602 in the image in Fig. 3 is small. 4, the bottom surface 44 of the heat shield 40 is far from the liquid surface L2, and the bottom surface 44 of the heat shield 40 reflects that the shadow of the liquid surface 602 is blocked by the heat shield 40. Therefore, the shaded area S2 on the liquid surface 602 in the image of Fig. 4 is large. Based on the foregoing principles, the image captured by the camera module 80 can be analyzed. The area of the shadow area corresponds to the distance between the liquid level 602 of the melt 60 and the bottom surface 44 of the heat shield 40.

Referring to FIG. 5, the image captured by the camera module 80 during the process of casting the body of the ingot 74 includes the lower half of the passage 42 of the heat shield 40 and the ingot 74. The body portion, the liquid surface 602 of the melter 60, and the bottom surface 44 of the heat shield 40 are reflected in the shaded area S3 of the liquid level 602. In the image of Fig. 5, the shaded area in the middle is blocked by the body of the ingot, so that there are two shaded areas S3 in the image. The subsequent steps of this embodiment are carried out in the process of casting the body of the ingot 74.

In the process of casting the body of the ingot 74, a plurality of different reference positions are first set, and then the second driving device 52 is driven to move the crucible 20 upward or downward to move the liquid surface 602 of the melt 60 to each The reference position, and recording the liquid level 602 at each of the reference positions, the distance between the liquid surface 602 of the melt 60 and the bottom surface 44 of the heat shield 40, and the two shadows in the image captured by the camera module 80 The area of the region S3 is formed to form a plurality of different reference distances and a plurality of different reference areas, wherein the reference distances are the liquid level 602 of the melt 60 at the reference positions, respectively, the liquid level 602 of the melt 60 The distance between the bottom surfaces 44 of the heat shields 40, which are formed by the liquid surface 602 of the melt 60 when the liquid level 602 of the melt 60 is respectively at the reference positions. The area of the shaded area. In the present embodiment, the area of the shaded area S3 is obtained by calculating the number of pixels of the shaded area S3 in the image.

Please refer to the following table, which is a comparison table between the position of the 坩埚 position and the number of pixels in the shadow area at the two reference positions, wherein the height of the 坩埚 position of the liquid level 602 is two at the reference position and the reference position, respectively. The data measured by the ruler (not shown), that is, the position of the 坩埚 is the height corresponding to the liquid level 602. Since the reference position 2 is higher than the reference position one, after the difference between the 坩埚 position and the difference in the number of pixels in the shadow area, it can be seen that the area of the shadow area S3 is increased by one pixel or decreased by 0.692 μm. In other words, For every 0.6292 μm increase in the distance between the liquid level 602 of the melt 60 and the bottom surface 44 of the heat shield 40, the number of pixels in the shaded area S3 in the image is increased by one, and vice versa. Thereby, in the stage of casting the body of the ingot 74, the change of the position of the liquid surface 602 of the melt 60 can be accurately obtained by the pixel change of the shaded area S3 in the image, and the resolution can reach 0.6292 μm/pixel.

Since the reference distances are proportional to the reference areas, an arithmetic expression can be established by performing linear regression operations on the reference distances and the reference areas, wherein the operation formula is: Gap=α×Area +β

Wherein, Gap is the distance between the liquid surface 602 of the molten soup and the bottom surface of the heat shield 40, and Area is the area of the shaded area formed by the heat shield 40 projected on the liquid surface 602, and α is a proportional value, β Is a constant.

The arithmetic expression is established in the control device 82 to form a correspondence for calculating the distance between the liquid surface 602 of the melt 60 and the bottom surface 44 of the heat shield 40.

Then, each time the crystal growth furnace 100 is casting the body of the ingot 74, the following steps can be performed: The control device 82 continuously acquires the image captured by the camera module 80, and analyzes the acquired image to determine the area of at least one shaded region S3 included in the image. In this embodiment, the control device 82 is configured. The area of the two shaded areas S3 on both sides of the body of the ingot 74 corresponds to the number of pixels in the two shaded areas S3 in the image.

The control device 82 causes the second driving device 52 to control the position of the crucible 20 in the vertical direction according to the area of the two shaded regions S3 to maintain the liquid surface 602 of the melt 60 and the bottom surface 44 of the heat shield 40. At a predetermined distance. In this embodiment, the calculation formula is substituted according to the area of the shaded area S3 in the image, and the area in the calculation formula is the area of the obtained shaded area S3 (ie, the number of pixels in the shaded area S3), and is calculated. The distance between the molten stone 60 liquid surface 602 and the bottom surface 44 of the heat shield 40 is obtained. Then, the control device 82 causes the second driving device 52 to change the position of the crucible 20 in the vertical direction according to the calculated distance, so that the liquid surface 602 of the melt 60 and the bottom surface 44 of the heat shield 40 are maintained between The predetermined distance.

By the above steps, each time the body of the ingot 74 is cast, the control device 82 can continuously acquire an image, and the liquid surface 602 of the melt 60 and the heat shield 40 are calculated from the area of the shaded area in the image. The distance between the bottom surfaces 44 is controlled to maintain the crucible 20 such that the liquid level 602 of the melt 60 and the bottom surface 44 of the heat shield 40 are maintained at the predetermined distance, so that the liquid surface 602 is in a stable thermal field. Thereby, the quality of the body of the ingot 74 is maintained constant from top to bottom.

In the foregoing, the distance is calculated by an arithmetic expression. In practice, the reference distances and the reference areas may be stored in a correspondence table and stored in the control device 82 to form a corresponding relationship. Then, the control device 82 compares the area of the shaded area S3 with the correspondence table to obtain the distance between the liquid surface 602 of the melt 60 and the bottom surface 44 of the heat shield 40.

In the above embodiment, the movement of the crucible 20 is controlled according to the distance between the liquid surface 602 and the bottom surface 44 of the heat shield 40 according to the area of the shaded area S3. The control of the molten liquid level position of the second preferred embodiment of the present invention will be described below. The method can also hold the position of the liquid level 602.

Please refer to FIG. 6 , the control method of the embodiment has the same steps as the first embodiment, except that the corresponding relationship is not established in the embodiment, but in the process of casting the body of the ingot 74 . The control device 82 continuously acquires the image captured by the camera module 80 (the same image as FIG. 5), and correspondingly determines the area of the at least one shaded region S3 included in the image according to the acquired image. Is the area of the two shaded area S3.

The control device 82 further controls the position of the second driving device 52 in the vertical direction according to the area of the two shaded regions S3, so that the total area of the two shaded regions S3 is maintained at a predetermined area. When the sum of the areas of the two shaded areas S3 is greater than the predetermined area, controlling the upward movement of the crucible 20 reduces the area of the two shaded areas S3 to maintain the predetermined area; the area of the two shaded areas S3 When the total is smaller than the predetermined area, the movement of the crucible 20 is controlled to increase the area of the two shaded areas S3 to maintain the predetermined area. In other words, the area of the shaded area S3 is maintained at the predetermined area, i.e., the distance between the liquid level 602 representing the melt 60 and the bottom surface 44 of the heat shield 40 is maintained constant, so that the liquid level is in a stable thermal field. The minimum amount of change in the liquid level position judged can also reach 0.6292 μm.

According to the above, the method for controlling the position of the molten liquid surface of the present invention can accurately determine the position of the molten liquid level in the sputum by monitoring the area of the shadow area in the image, thereby accurately controlling the movement of the sputum and allowing the casting During the process of the body of the ingot, the liquid surface is in a stable thermal field, so that the quality of the body of the ingot is maintained from top to bottom.

The above is only a preferred embodiment of the present invention, and equivalent changes to the scope of the present invention and the scope of the patent application are intended to be included in the scope of the present invention.

Claims (10)

A method for controlling the position of a molten liquid surface is applied to a crystal growth furnace, wherein the crystal growth furnace includes a crucible and a heat shield disposed above the crucible, the crucible is for containing a melting furnace, and the heat shield has an opening The control method includes the following steps: A. providing a photographic module, the photographic module picking up an image of the liquid level of the simmering soup from the opening of the opening of the heat absorbing cover, and the image Included in the at least one shaded area formed by the liquid cover projected on the liquid surface of the molten soup; B, obtaining an image captured by the camera module, and determining the image included in the image according to the acquired image The area of the shaded area, wherein the area of the shaded area corresponds to the distance between the liquid surface of the molten soup and the bottom surface of the heat shield; C, according to the area of the shaded area, the position of the horizontal direction is controlled to melt The liquid level of the soup is maintained at a predetermined distance from the bottom surface of the heat shield. The method for controlling the position of the molten liquid surface according to claim 1, wherein the step C is based on the area of the shaded area corresponding to a distance between the bottom surface of the heat shield and the molten liquid surface, and then the distance is controlled according to the distance. The position in the vertical direction maintains the predetermined distance between the liquid level of the melt and the bottom surface of the heat shield. The method for controlling the position of the molten liquid surface according to claim 2, wherein the step B further comprises establishing a correspondence between the plurality of different reference distances and the plurality of different reference areas, wherein the reference distances are melted The distance between the liquid level of the molten soup and the bottom surface of the heat shield when the liquid level is respectively at different reference positions, and the reference areas are the liquid levels of the molten soup respectively at the reference positions, the heat shield The area of the shaded area formed by the liquid surface of the molten soup is projected; in step C, the distance between the molten liquid surface and the bottom surface of the heat shield is obtained according to the corresponding relationship between the area of the shaded area and the corresponding relationship. The method for controlling the position of the molten liquid surface according to claim 3, wherein the step B includes performing a linear regression operation on the reference distances and the reference areas to establish an operation formula, and the operation formula constitutes the correspondence relationship. Wherein the calculation formula is: Gap=α×Area+β, wherein Gap is the distance between the liquid surface of the melt and the bottom surface of the heat shield, and Area is the shadow formed by the heat shield projected on the liquid surface. The area of the area, α is the proportional value, and β is a constant; in step C, the Area in the expression is the area of the shaded area in the image to calculate the distance. The method for controlling the position of the molten liquid surface according to claim 3, wherein before step B, the reference distances are formed into a correspondence table with the reference areas, and the correspondence table constitutes the correspondence relationship; The area of the shaded area in the image is compared to the corresponding table to obtain the distance. The method for controlling the position of the molten liquid surface according to claim 1, wherein in step B, the area of the shaded area is corresponding according to the number of pixels of the shaded area in the image. A method for controlling the position of a molten liquid surface is applied to a crystal growth furnace, wherein the crystal growth furnace includes a crucible and a heat shield disposed above the crucible, the crucible is for containing a melting furnace, and the heat shield has an opening Corresponding to the inside, the molten soup in the crucible is used for casting a crystal rod; the control method comprises the following steps: A. providing a photography module, the photography module is obliquely above the opening of the heat shield. Taking an image of the liquid surface of the melted soup, and the image includes at least one shaded area formed by the heat shield projected on the liquid surface of the melt; B, in the process of casting the body of the ingot, Continuously obtaining the image captured by the camera module, and according to the acquired image, corresponding to the area of the shaded area included in the image, Wherein the area of the shaded area corresponds to the distance between the liquid surface of the molten soup and the bottom surface of the heat shield; C. controlling the position of the horizontal direction in the shaded area according to the area of the shaded area in the image, so that the shaded area The area is maintained at a predetermined area. The method for controlling the position of the molten liquid surface according to claim 7, wherein in step B, the area of the shaded area is corresponding according to the number of pixels of the shaded area in the image. The method for controlling the position of a molten liquid surface according to claim 7, wherein in step C, the area of the shaded area in the image is compared with the predetermined area, and when the area of the shaded area is larger than the predetermined area, the control is performed. The upward movement of the weir reduces the area of the shaded area to maintain the predetermined area. The method for controlling the position of the molten liquid surface according to claim 7, wherein in step C, the area of the shaded area in the image is compared with the predetermined area, and when the area of the shaded area is smaller than the predetermined area, the control is performed. The movement of the crucible moves the area of the shaded area to maintain the predetermined area.