JP2003176199A - Apparatus and method for pulling single crystal - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an apparatus for pulling a single crystal having a tail part of a desired shape by exactly measuring the weight of the single crystal by correcting measured values, and to provide a method therefor. <P>SOLUTION: In the single crystal pulling apparatus using the Czochralski method, the control of the crystal diameter of up to the cylindrical part of the single crystal is carried out by controlling a pulling speed with a control device according to crystal diameter image signals from a two-dimensional camera, and the control of the crystal diameter of the tail part is carried out by controlling the pulling speed with the control device according to crystal weight signals from a load cell. The method for pulling the single crystal comprising such processes is also provided. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a single crystal pulling apparatus and a single crystal pulling method, and more particularly to a single crystal for controlling a crystal diameter by correcting a single crystal weight value measured by a load cell by using the Czochralski method. The present invention relates to a pulling device and a pulling method.

[0002]

2. Description of the Related Art Silicon wafers used for semiconductor devices are manufactured by slicing a silicon single crystal pulled by the Czochralski method (CZ method). When pulling this single crystal, the crystal shape is controlled by imaging the crystal growth region with a two-dimensional camera, etc. through the camera port provided in the body of the pulling device, and based on the diameter signal, the power supplied to the heater and the single crystal. This is done by adjusting the pulling conditions with the pulling speed as a parameter.

To finish pulling a single crystal,
A process called a tail diaphragm that gradually reduces the crystal diameter is required to prevent the graded conversion due to thermal strain.However, when adjusting the conditions of an optical system that uses a two-dimensional camera, a single aperture with a large diameter is used. The crystal growth region in the drawing process of the tail portion of the inverted conical shape of the crystal cannot be reliably imaged, and the pulling condition is adjusted by measuring the crystal weight.

In the conventional weight measurement of a silicon single crystal, like a single crystal pulling apparatus described in Japanese Patent Laid-Open No. 62-72589, the weight is measured by a load cell through a rotating pulling shaft, and pulling conditions are adjusted. It is used to do.

However, the method of utilizing the weight data described in this publication is merely a monitor, and it is impossible to accurately measure the weight of the single crystal to grow a tail portion having a desired shape.

[0006]

Therefore, there is a demand for a single crystal pulling apparatus and a pulling method capable of accurately measuring the weight of a single crystal by correcting the measured value and growing a tail portion having a desired shape. It had been. The present invention has been made in consideration of the above circumstances, by accurately measuring the weight of the single crystal by correcting the measurement value, a single crystal pulling device capable of growing a tail portion of a desired shape, and The purpose is to provide a pulling method.

[0007]

In order to achieve the above object, according to one aspect of the present invention, in a single crystal pulling apparatus for pulling a single crystal using the Czochralski method, a silicon melt and growth are performed. A two-dimensional camera that images the boundary with the single crystal, a load cell that measures the weight of the single crystal through a wire for pulling the single crystal, and a single crystal that receives a crystal information signal from the load cell and the two-dimensional camera Having a control device for controlling the pulling speed, the crystal diameter control up to the straight body part of the single crystal is performed by controlling the pulling speed by the control device based on the crystal diameter image signal from the two-dimensional camera, There is provided a single crystal pulling device characterized in that the crystal diameter is controlled by controlling the pulling speed by the control device based on the crystal weight signal from the load cell. As a result, the weight of the single crystal is accurately measured, the tail portion having a desired shape is grown, and the entire single crystal is grown to have a desired shape.

In a preferred example, the diameter control of the tail portion is performed by load cell arithmetic processing means provided in the control device based on the crystal weight data obtained by subtracting the surface tension of the solid-liquid interface from the weight value measured by the load cell. Do it by controlling the speed. This allows an accurate weight value to be used and the desired tail to be grown.

In another preferable example, the tail diameter is controlled by calculating the tail diameter from the weight data and controlling the pulling speed with reference to a preset tail diameter change. As a result, the desired tail portion is grown.

According to another aspect of the present invention, in the single crystal pulling method using the Czochralski method, the diameter of the single crystal is controlled by subtracting the surface tension of the solid-liquid interface from the weight value measured by the load cell. There is provided a single crystal pulling method characterized in that the pulling speed is controlled based on crystal weight data. Thereby, the diameter of the single crystal is accurately controlled.

In a preferred example, the diameter control of the single crystal is diameter control of the tail portion of the single crystal. This allows
The control of the diameter of the tail is done accurately.

Further, according to another aspect of the present invention, in the single crystal pulling method using the Czochralski method, the diameter control of the single crystal up to the straight body part is performed by a crystal diameter image signal from a two-dimensional camera. The pulling speed is controlled based on
There is provided a method for pulling a single crystal characterized in that the diameter of the tail portion is controlled based on a crystal weight signal from the load cell. As a result, the weight of the single crystal is accurately measured, the tail portion having a desired shape is grown, and the entire single crystal is grown to have a desired shape.

In a preferred example, the diameter of the tail portion is controlled by controlling the pulling speed with reference to a measured weight value measured in advance for a predetermined shape. As a result, the desired tail portion is grown.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of a single crystal pulling apparatus according to the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a conceptual diagram of a single crystal pulling apparatus according to the present invention.

As shown in FIG. 1, the apparatus 1 for pulling a single crystal according to the present invention melts a water-cooled furnace body 2 and a raw material polysilicon contained in the furnace body 2 to melt silicon M.
The quartz crucible 3 having the above structure, the graphite crucible 4 that holds the quartz crucible 3, and the heater 5 that surrounds the graphite crucible 4. The graphite crucible 4 penetrates through the furnace body 2, is coupled to a crucible rotation motor 6, is rotated, and is attached to a crucible rotation shaft 8 which is moved up and down by an elevating device 7.

Further, above the quartz crucible 3, there is provided a pulling wire 11 to which a seed chuck 10 for holding a seed 9 for pulling a single crystal is attached. This wire 11 is a furnace body 2. The wire winding device 12 is provided on the outer upper part and is rotated by a motor (not shown) to pull up the single crystal Ig while rotating and pulling it up.

Further, the outer wall of the shoulder 2a of the furnace body 2 is provided with a camera port 13 capable of transmitting light by closing the through hole with heat resistant glass. A two-dimensional camera 14 having an optical axis penetrating the camera port 13 is provided outside the furnace body 2, and its focus is set in the single crystal growth region.

The two-dimensional camera 14 has an AD conversion circuit 15
, And the crystal diameter signal from the two-dimensional camera 14 is
It is adapted to be transmitted to the D conversion circuit 15. This A
The crystal diameter signal is binarized by the D conversion circuit 15, transmitted to the image processing device 16, image-processed by the image processing device 16 and selectively output as crystal diameter data to the control device 18 via the changeover switch 17. It

Further, the wire winding device 12 is provided with a load cell 19, which is connected to an amplifier 20 for amplifying the crystal weight signal which is the output of the load cell 19. Further, the amplifier 20 outputs its output. It is connected to an AD conversion circuit 21 for digitization and is selectively output as crystal weight data to the control device 18 via the changeover switch 17.

The crystal diameter image signal obtained from the two-dimensional camera 14 is output to the control device 18 at the time of pulling up the neck portion N, the crown portion C, and the straight body portion B during the pulling process shown in FIG. Changeover switch 17 when raising T
And the crystal weight signal obtained from the load cell 19 is output to the controller 18. This control device 1
Switching from the crystal diameter image signal output to 8 to the crystal weight signal is programmed in the control device 18 in advance, and when the growing process of the tail portion T is started, the control device 18 sends a switching signal to the switch controller 17c. It is done by sending.

As the control device 18, a general computer is used, and the two-dimensional camera arithmetic processing unit 50a for processing the crystal diameter data from the two-dimensional camera 14 and the load cell 1 are used.
Load cell arithmetic unit 1 for processing crystal weight data from 9
8b and a memory 18 provided with a table memory 18c
d, the two-dimensional camera operation unit 18a, the load cell operation unit 1
8b and control means 18 for controlling each controller to be described later, and the table memory 18c stores in the table memory 18c density information of silicon, shape information of crystal, pulling speed necessary for forming the shape, heater input, crucible rotation speed. The optimum conditions for the crucible ascending speed are preset and stored. The various data and the like of the optimum pulling conditions are composed of the optimum values which are respectively obtained corresponding to various crystal shapes theoretically or by past experience or experiments.

As a control system for actually controlling these, the control device 18 controls the changeover switch controller 17c for controlling the changeover switch 17 and the power supply amount of the heater 5 for controlling the temperature of the silicon melt. Heater controller 5c,
A motor controller 6c for controlling the rotation speed of the quartz crucible 3, a lifting device controller 7c for controlling the height of the quartz crucible 3, a wire winding device controller 12c for controlling the pulling speed and the rotation speed of the crystal, etc. are connected. ing. Each of these controllers 6c,
7c, 12c, etc. are controlled to change the pulling conditions and control the diameter of the crystal.

Next, a method for pulling a silicon single crystal using the single crystal pulling apparatus according to the present invention will be described.

Polysilicon is placed in the quartz crucible 3 and pulling is automatically performed by a programmed pulling process. At this time, the two-dimensional camera 14 moves the neck growth area A
n, for example, the focus is focused on the position deviated from the center of the quartz crucible 3 to the outside by 3 mm, and the image pickup power is turned on from the start of pulling.

After the preparation for pulling is completed, for example, argon gas is introduced into the furnace body 2 from above the furnace body 2, the heater 5 is energized to heat the quartz crucible 3, and the crucible rotation motor 6 is energized to rotate the crucible. The crucible rotating shaft 8 connected to the motor 6 is rotated to rotate the quartz crucible 3.

After a lapse of a certain time, the wire 11 is lowered and the seed 9 is brought into contact with the liquid surface of the silicon melt M to be blended.

Thereafter, pulling is started, and the neck growth region An is monitored by the two-dimensional camera 14 as shown in FIG. 3 (a).

As shown in FIG. 1, this two-dimensional camera 14
2 is transmitted to the AD conversion circuit 15 and the crystal diameter image information of
It is digitized, image-processed by the image processing device 16, and sent to the control device 18 shown in FIG. 2 as crystal diameter image data via the changeover switch 20, and by the normally used two-dimensional camera operation part 18a of this control device 18. , The net value of the diameter is calculated, the amount of change in the diameter is calculated and compared with the amount of change in the diameter stored in the table memory 18c, and the controller 18e causes the heater controller 5c and the motor controller 6 to operate.
c, the lifting device controller 7c, and the wire winding device controller 12c, and the neck N has a constant length, for example, 3
The pulling is continued up to 00 mm.

When the neck N reaches 300 mm, the heater controller 5c and the motor controller 6 are transmitted via the controller 18 by the process program incorporated in the memory 18d.
c, the elevating device controller 7c, and the wire winding device controller 12c are controlled, and the pulling of the single crystal starts the step of growing the crown C shown in FIG. 3 (b).

Subsequently, the crown growth region _AC is monitored by the two-dimensional camera 14, and the image signal from the two-dimensional camera 14 is converted into the AD conversion circuit 15, the changeover switch 20, the image processing apparatus as shown in FIG. Control device 1 through 16
Sent to 8. The same calculation processing is performed by the two-dimensional camera calculation control means 50a, and the heater controller 5c, the motor controller 6c, the lifting device controller 7c, and the wire winding device controller 12c are controlled by the output from the control device 20d. Then, the pulling condition is controlled so that the diameter of the growing crystal gradually increases and the crown C is formed.

Further pulling is continued to grow the crown C, and when the diameter of the crown C reaches 310 mm, for example, based on the crystal diameter image information from the two-dimensional camera 14, the AD conversion circuit 15, the image processing. The crystal diameter image data is input to the two-dimensional camera arithmetic control means 50a via the device 16 and the changeover switch 20, arithmetic processing is performed, and the heater controller 5c, the motor controller 6c, and the lifting device controller are controlled via the control means 21. 7c, and wire winding device controller 12
Controlling c and keeping the diameter of the crystal constant, pulling up of the single crystal enters the step of growing the straight body portion D shown in FIG. The two-dimensional camera 14 monitors the straight body part growth region A _D , maintains the growing condition of the straight body part D, forms a straight body part of a predetermined length, and completes pulling.

When the straight body portion is formed and the pulling up is completed, the step of growing the tail portion T is started.

The step of growing the tail portion T is an operation of narrowing the crystal diameter, but the two-dimensional camera 24 cannot image the tail portion growth region _AT . So load cell 19
Using the change of the crystal weight as a data, the tail diameter T is grown by controlling the crystal diameter.

Therefore, the control means 10 turns off the two-dimensional camera 14, controls the changeover switch controller 17c to change over the changeover switch 17, and the crystal weight signal detected by the load cell 19 is amplified by the amplifier 20 and the AD conversion circuit 2.
It is output to the control device 18 as crystal weight data via 1. As a control method to control the pulling speed,
PID and fuzzy control are preferred.

The crystal weight data output to the controller 18 is processed by the load cell arithmetic processing means 20b as follows.

For example, at the boundary portion b (solid-liquid interface) between the silicon melt M dissolved in the quartz crucible 2 and the solid single crystal Ig, a suction force is generated by the surface tension of the melt M. A crystal weight value larger than the actual crystal weight value is output from the load cell 19.

The surface tension at this time can be obtained as follows.

As shown in FIG. 4, the diameter of each part of the single crystal pulled up by manual operation, for example, every 10 mm is measured with a caliper or the like. The weight value for each site (interval) is calculated by the formula (1).

Next, at the time of pulling up the single crystal, from the crystal weight value W _{(Tn )} measured and recorded by the load cell, the above formula (1) is obtained.
The surface tension γ _(Tn) for each site (interval) is calculated by subtracting the W _(n) calculated in.

The surface tension obtained as described above is stored in the table memory 18c.

The net weight at the tail portion T is calculated based on the surface force thus stored, and the pull-up control is fed back.

In the diameter control at the tail, the crystal diameter is calculated based on the weight data by using the following calculation formula, and the pulling speed is controlled in comparison with the preset change in the tail diameter. .

The crystal diameter at the tail is calculated by the weight calculation formula (1).

[Equation 1] From this, the radius r ₂ is obtained by taking r ₁ as the radius at the time of transition to the tail (1/2 of the value measured by the analyzer (camera)).

[0045]

[Equation 2] According to the growth of the tail portion, r ₃ and r ₄ are sequentially calculated from the equation (2).

FIG. 5 shows the tail portion T using the load cell 19.
A main flow of data processing for diameter control in FIG. 5 is shown, and a single crystal diameter control method will be described with reference to FIG.

The load cell crystal weight data W _(Ln) is measured by the load cell 19 (ST1).

The net weight value W _(Tn) of the tail weight is calculated (ST2).

This net weight value W _(Tn) is calculated using the following equation (3).

[0050]

[Equation 3] The tail diameter (D _(Tn) ) is obtained from this equation (3).

If tail diameter D _(Tn) <set value D _T ,
The control device 18 controls the winding device 20 via the wire winding device controller 12c to reduce the pulling speed.
On the other hand, if the tail diameter D _(Tn) > the set value D _T , the pulling speed is increased.

Also in the growing process of the tail portion T, the pulling speed is controlled by controlling the winding device 20 via the control device 18 and the wire winding device controller 12c by the process program incorporated in the memory 18d. The heater controller 5c and the motor controller 6 as required.
The heater 5, the crucible rotation motor 6, and the lifting device 7 are controlled via the c and lifting device controller 7c to grow the tail portion T.

In the step of growing the tail portion as described above, an accurate weight value can be used by correcting the weight of the pulled single crystal in consideration of the surface tension, and the desired tail portion is grown. be able to.

In the above embodiment, the diameter of the single crystal up to the straight body is controlled by controlling the pulling speed based on the crystal diameter image signal from the two-dimensional camera, and the diameter of the tail is controlled by the load cell. Although it has been described in the example based on the crystal weight signal from, the single crystal pulling method according to the present invention is not limited to the growing step of the tail portion, and if necessary,
It can also be used in the growing process of pulling a single crystal. It becomes possible to measure the diameter of a single crystal without using a two-dimensional camera.

[0055]

According to the single crystal pulling apparatus and pulling method according to the present invention, the weight of the single crystal can be accurately measured by correcting the measured value, and the tail portion having a desired shape can be grown. A single crystal pulling apparatus and pulling method can be provided.

[Brief description of drawings]

FIG. 1 is a conceptual diagram of a single crystal pulling apparatus according to the present invention.

FIG. 2 is a conceptual diagram of a control device used in the single crystal pulling apparatus according to the present invention.

FIG. 3 is a conceptual diagram showing a crystal information signal acquisition method in the single crystal pulling method according to the present invention.

FIG. 4 is a conceptual diagram showing a method of calculating a weight value for each site (interval) of a single crystal in the single crystal pulling method according to the present invention.

FIG. 5 is a flowchart showing a main flow of data processing for diameter control in the tail portion in the single crystal pulling method according to the present invention.

[Explanation of symbols]

1 Single crystal pulling device 2 furnace body 2a shoulder 3 Quartz crucible 4 Graphite crucible 5 heater 5c heater controller 6 Crucible rotation motor 6c Motor controller 7 Lifting device 7c Lifting device controller 8 crucible rotation axis 9 seeds 10 seed chuck 11 wires 12 Wire winding device 12c Wire winding device controller 13 camera port 14 two-dimensional camera 15 AD conversion circuit 16 Image processing device 17 Changeover switch 17c Changeover switch controller 18 Control device 18a Two-dimensional camera operation unit 18b Load cell operation unit 18c table memory 18d memory 18e control unit 19 load cell 20 amps 21 AD conversion circuit Ig single crystal M Molten Silicon

Claims (8)

[Claims] 1. A single crystal pulling apparatus for pulling a single crystal using the Czochralski method, comprising a two-dimensional camera for imaging a boundary portion between a silicon melt and a growing single crystal, and a wire for pulling the single crystal. A load cell for measuring the weight of a single crystal through, and a control device for controlling a single crystal pulling speed by receiving a crystal information signal from the load cell and the two-dimensional camera, and a crystal diameter up to a straight body portion of the single crystal. The control is performed by controlling the pulling speed by the control device based on the crystal diameter image signal from the two-dimensional camera, and the crystal diameter control of the tail portion is performed by the control device based on the crystal weight signal from the load cell. A single crystal pulling device characterized by being controlled. 2. The single crystal pulling apparatus according to claim 1, wherein the diameter of the tail portion is controlled by a load cell arithmetic processing means provided in the control device from the weight value measured by the load cell to the surface tension of the solid-liquid interface. A single crystal pulling apparatus, wherein the pulling speed is controlled based on the crystal weight data obtained by subtracting. 3. The single crystal pulling apparatus according to claim 2, wherein the diameter of the tail portion is controlled by calculating the tail diameter from the weight data and referring to a preset change in the tail diameter to set the pulling speed. A single crystal pulling device characterized by being controlled. 4. In the single crystal pulling method using the Czochralski method, the diameter of the single crystal is controlled by controlling the pulling rate based on the crystal weight data obtained by subtracting the surface tension of the solid-liquid interface from the weight value measured by the load cell. And a single crystal pulling method. 5. The method for pulling a single crystal according to claim 4, wherein controlling the diameter of the single crystal is controlling the diameter of a tail portion of the single crystal. 6. In a single crystal pulling method using the Czochralski method, the diameter of the single crystal up to the straight body is controlled by controlling the pulling speed based on a crystal diameter image signal from a two-dimensional camera. The method for pulling a single crystal is characterized in that the diameter of the portion is controlled based on the crystal weight signal from the load cell. 7. The method for pulling a single crystal according to claim 6, wherein the diameter of the tail portion is controlled by controlling the pulling rate based on crystal weight data obtained by subtracting the surface tension of the solid-liquid interface from the weight value measured by the load cell. And a single crystal pulling method. 8. The single crystal pulling method according to claim 5, wherein the diameter control of the tail portion is performed by referring to a measured weight value previously measured for a predetermined shape. A method for pulling a single crystal, characterized in that the speed is controlled.