KR101571958B1 - Apparatus and method for growing ingot - Google Patents

Abstract

The ingot growing apparatus of the present invention includes a chamber for providing a space required for an ingot growing process; A quartz crucible for holding a silicon melt with a heat resistant container disposed in the chamber; A heater for heating the quartz crucible; A seed chuck for fixing a seed for pulling up the ingot from the silicon melt; A seed upstanding part for immersing the seed chuck in the silicon melt and simultaneously raising the seed chuck; A heat shield for forming a melt gap with the upper side heat insulating means of the silicon melt; A diameter sensor for measuring the diameter of the ingot being pulled up; A melt gap sensor for measuring the melt gap; A temperature sensor for measuring the temperature of the silicon melt; And a temperature controller receiving the actual temperature and melt gap measured from the temperature sensor and the melt gap sensor, and controlling the heater according to the designed target temperature profile and the actual temperature and the melt gap.
According to the present invention, the actual temperature in the ingot growing apparatus can be precisely controlled, thereby maintaining the diameter of the ingot uniform and improving the crystal quality.

Description

[0001] Apparatus and method for growing ingot [0002]

The present invention relates to an ingot growing apparatus and an ingot growing method which produce a high-quality ingot through appropriate temperature control.

Silicon wafers, which are mainly used as substrates in the manufacture of semiconductor devices, generally have high-purity polycrystalline silicon produced, and then monocrystals are grown from polycrystalline silicon according to the Czochralski (CZ) crystal growth method, The wafer is sliced to produce a silicon wafer. The wafer is mirror-polished, cleaned, and finally inspected.

For example, in the conventional single crystal ingot growing method, after a seed is immersed in a melt in which polycrystalline silicon is melted, the seed crystal is grown at a high pulling rate to proceed the necking process. Then, the single crystal is gradually grown in the radial direction with the seed, and if the seed crystal has a predetermined diameter, the shouldering step is performed. The body growth is performed after the shouldering step, the body is processed for a predetermined length, the diameter of the body is decreased, and the single crystal ingot growth is completed through a tailing process in which the body is separated from the melt.

The main interest in single crystal growth in such a Chrystalski process lies in preventing the formation of dislocations, voids or other defects in the crystal lattice structure. If local defects or dislocations propagate in the single crystal, the whole single crystal can not be used at all.

Particularly, when the single crystal ingot is grown by the Czochralski process, vacancies and interstitial silicon are introduced into the single crystal through the solid-liquid interface. When the concentration of the introduced vacancies and interstitial silicon is supersaturated State, silicon diffuses and coheres between vacancies and interstitials to form vacancy defects (hereinafter referred to as V defects) and interstitial defects (called I defects).

In order to suppress the occurrence of V defects and I defects, a method of controlling the ratio V / G of the pulling rate V of the single crystal and the temperature gradient G at the liquid interface is controlled within a specific range. The pulling rate of the single crystal and the temperature at the solid-liquid interface also correspond to the factors determining the ingot diameter of the single crystal.

Therefore, in order to suppress the occurrence of defects in the ingot and to keep the diameter uniform, it is necessary to appropriately control the temperature of the silicon melt with the pulling rate.

Conventionally, in order to appropriately control the temperature of the melt, the target temperature profile is redesigned in consideration of the target temperature profile used in the previous batch and the controlled actual temperature, The process was carried out.

However, when the ingot growth process is performed with the target temperature profile thus redesigned, the actual temperature can not be precisely controlled to the desired target temperature.

This is because the target temperature profile is designed only considering the relationship between the heater power and the actual temperature, and thus does not reflect a change in the other factors involved in the actual temperature.

In order to reduce such an error, conventionally, after the temperature deviation has occurred, the matching ratio between the target temperature and the actual temperature has been raised through feedback control for correcting the target temperature. However, since the correction is performed after the deviation has already occurred, There was a limit to height.

In addition, the temperature can not be controlled to a desired value due to the deviation between the target temperature and the actual temperature. As a result, the diameter of the ingot is not uniform and defects are generated.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and it is an object of the present invention to provide a feed forward method for advancing an ingot growing process to a target temperature designed in consideration of a melt gap and correcting a target temperature in advance according to a change in melt gap, The present invention also provides an ingot growing apparatus and method which can precisely control an actual temperature through control.

An ingot growing apparatus according to the present invention includes: a chamber for providing a space necessary for an ingot growing process; A quartz crucible for holding a silicon melt with a heat resistant container disposed in the chamber; A heater for heating the quartz crucible; A seed chuck for fixing a seed for pulling up the ingot from the silicon melt; A seed upstanding part for immersing the seed chuck in the silicon melt and simultaneously raising the seed chuck; A heat shield for forming a melt gap with the upper side heat insulating means of the silicon melt; A diameter sensor for measuring the diameter of the ingot being pulled up; A melt gap sensor for measuring the melt gap; A temperature sensor for measuring the temperature of the silicon melt; And a temperature controller receiving the actual temperature and melt gap measured from the temperature sensor and the melt gap sensor, and controlling the heater according to the designed target temperature profile and the actual temperature and the melt gap.

In addition, the ingot growing method according to the present invention includes the steps of: progressing the ingot growing process with the redesigned target temperature profile in accordance with the change of the target melt-gap profile; Periodically measuring the actual temperature and melt gap of the silicon melt during the process; Correcting the target temperature profile according to the difference between the measured melt gap and the target melt gap profile; Proceeding the remaining ingot growth process with the corrected target temperature profile; And a control unit.

The present invention is advantageous in that the temperature in the ingot growing apparatus can be precisely controlled by considering the melt gap as a temperature control element.

Further, there is an advantage that the diameter of the ingot can be uniformly maintained through precise temperature control and the crystal quality can be improved.

1 shows a schematic view of an ingot growing apparatus according to an embodiment of the present invention.
2 is a flowchart illustrating a process of controlling a temperature in consideration of a melt gap according to an embodiment of the present invention.
FIG. 3 shows a temperature correction value according to the amount of change in the melt gap, according to an embodiment of the present invention.
Figure 4 shows a previous target melt-gap profile and a redesigned current target melt-gap profile, according to an embodiment of the present invention.
Figure 5 shows a draft of the target temperature profile and a corrected target temperature profile, in accordance with an embodiment of the present invention.
FIG. 6 is a graph showing a comparison example in which the temperature is controlled without considering the change of the melt gap, and a difference between this embodiment in which the temperature is controlled in consideration of the melt gap.

Hereinafter, the present embodiment will be described in detail with reference to the accompanying drawings. It should be understood, however, that the scope of the inventive concept of the present embodiment can be determined from the matters disclosed in the present embodiment, and the spirit of the present invention possessed by the present embodiment is not limited to the embodiments in which addition, Variations.

1 shows a schematic view of an ingot growing apparatus according to an embodiment of the present invention.

1, the ingot growing apparatus according to the present embodiment includes a chamber 10 for providing a space required for a process, a quartz crucible 20 for accommodating a silicon melt, and a quartz crucible 20 A side heat insulating part 80 which is a heat insulating means disposed on the side surface of the heater 40 and a heat shielding part 80 which forms a melt gap by the heat insulating part disposed above the silicon melt, A seed chuck 60 for fixing a seed for pulling up the ingot from the silicon melt and a seed chuck 60 through a pull cable connected to the seed chuck 60. [ And a pulling system 400 for rotating and lifting the seed.

In particular, the ingot growing apparatus of the present embodiment includes a view port 500 for transmitting light in a sealed chamber 10, a melt gap sensor 200 for measuring a melt gap through the view port, (70) connected to the melt-gap sensor (200) and the temperature sensor (70) to receive the measured data and to receive the measured temperature profile together with a predetermined target temperature profile And a temperature controller (100) for controlling the heater (40) in consideration of the measured data.

To explain each component in more detail, first, the chamber 10 provides a space in which predetermined processes for growing the wafer ingot are performed.

A quartz crucible 20 containing a silicon melt as a heat resistant container made of quartz is disposed in the chamber 10 and a graphite crucible 30 supporting the quartz crucible 20 is provided on the outer periphery of the quartz crucible 20. A supporting means for supporting a load is placed on the lower portion of the graphite crucible 30. The quartz crucible 20 is coupled to a pedestal to which the crucible rotating portion 90 is connected so that the quartz crucible 20 can be raised and lowered simultaneously with rotation.

The seed chuck 60 equipped with the seed for growing an ingot from the silicon melt contained in the quartz crucible 20 is connected to the seed cable and disposed above the quartz crucible 20. The seed up- The seed chuck 60 can be raised and lowered simultaneously with the rotation by adjusting the winding direction of the seed cable. That is, the seed upstanding part 400 can raise the ingot by lowering the seed chuck 60 to immerse the seed in the silicon melt and then raise it simultaneously with rotation.

A heater 40 for supplying thermal energy is disposed on the outer side of the quartz crucible 20 to melt polysilicon and a heat is applied to the side of the ingot growing apparatus The side heat insulating portion 80, which is insulated so as not to leak, is composed of the heat shielding and the side insulating material.

For example, a cylindrical heater 40 having a hollow to surround the quartz crucible 20 is disposed outside the quartz crucible 20 by a predetermined distance, and likewise, The side heat shielding portion 80 may be provided outside the heater 40.

In order to prevent heat loss of the silicon melt contained in the quartz crucible 20, a heat shield 50, which is a heat insulating means having a hollow through which the ingot to be grown passes, is disposed above the quartz crucible 20. [

At this time, the shortest distance between the heat shield 50 and the surface of the silicon melt is defined as a melt gap, and the melt gap can be utilized as an index indicating the heat energy lost in the silicon melt.

That is, as the melt gap is small, the amount of heat to be shielded is large, so that the loss of heat energy is reduced, and the actual temperature of the silicon melt will be high. When the malt gap is large, the amount of heat shielded decreases, Since the actual temperature can be predicted to be lowered, the melt gap can be considered together with the heater power in the subsequent temperature control.

On the other hand, in order to observe the inside of the sealed chamber 10, a view port 500 for transmitting light inside the chamber 10 is provided on one side of the chamber 10.

Image sensors 200 and 300 are disposed outside the chamber 10 to measure process progress through the view port 500.

In the image sensor, the brightness of the meniscus of the ingot to be grown is measured, and the diameter of the ingot is converted into the ADC value. Then, the preset target ADC value is compared with the measured current ADC value to control the pulling speed, An ADC sensor 300 for controlling the diameter of the melt gap sensor 200, and a melt gap sensor 200 for measuring the melt gap.

The melt gap sensor 200 measures the melt gap in real time and transmits the measured melt gap to the crucible rotation unit 90. The crucible rotation unit 90 compares the measured melt gap with a designed target melt gap profile Thereby controlling the crucible lifting speed, thereby maintaining the measured melt gap at the target melt gap.

Here, the target melt-gap profile refers to the target melt-gap history to be maintained as the process progresses. The target melt-gap profile refers to the target melt- Designed before.

A temperature sensor 70 is provided at one side of the heater 40 or the side surface heat insulating part 200 to measure the actual temperature of the surrounding environment and transmits the measured actual temperature to the temperature controller 100.

The temperature controller 100 is connected to the temperature sensor 70 and the heater 40 to compare the actual temperature with the target temperature profile to control the thermal energy applied by the heater 40.

In this case, the target temperature profile means a target temperature at which the actual temperature should be reached in accordance with the process progress time, and the quality of the ingots, the pulling rate, the heater power, the actual temperature and the previous target temperature profile, And designed before the process.

However, as described above, the temperature of the silicon melt can be greatly influenced not only by the heat energy transferred by the heater 40 but also by the melt gap.

That is, since the amount of heat loss of the silicon melt is changed according to the variation of the melt gap, the actual temperature of the silicon melt to be changed can be precisely controlled in consideration of the thermal energy lost by the heater 40 and the lost heat energy.

The present embodiment intends to precisely control the actual temperature to the desired target temperature through the feedforward temperature control in consideration of the fact that the actual temperature changes in accordance with the change of the melt gap.

Hereinafter, the feedforward temperature control of the present embodiment will be described in detail with reference to Figs. 2 to 5. Fig.

FIG. 2 is a flowchart illustrating a process of controlling a temperature in consideration of a melt gap, according to an embodiment of the present invention, and FIG. 3 shows a temperature correction value according to a change amount of a melt gap according to an embodiment of the present invention.

In order to control the feed forward temperature in consideration of the melt gap, first, the temperature control unit 100 redesigns the target temperature profile from the data of the previous batch. (S101)

The data of the previous batch may correspond to the previous target temperature profile, the heater power according to the previous target temperature profile, and the actually measured temperature history in the process, and in particular, the target melt gap profile change amount is further included in this embodiment.

 That is, in this embodiment, the draft of the target temperature profile is designed in consideration of the previous target temperature profile and the actual measured temperature history, and then the target temperature profile draft is calculated by taking into consideration the amount of change of the previous target melt gap and the redesigned target melt gap The target temperature profile is redesigned as a correction method.

The target temperature profile draft design is a conventionally used design method and it is obvious to a person skilled in the art that the description thereof will be omitted. Hereinafter, a method of redesigning and correcting the target temperature profile draft will be described in detail.

Referring to FIG. 3, the graph shows the correction value of the target temperature corresponding to the change of the melt gap, and the target temperature profile can be redesigned on the basis of the correction value.

That is, in the target temperature profile redesign of the present embodiment, if the target melt gap at a certain point of time is smaller than the previous target melt gap, the actual temperature will be low because there is little thermal energy to be lost. On the contrary, if the target melt-gap at another point of time is larger than the previous target melt-gap, the actual temperature will be lower due to a large amount of heat energy lost.

For example, if the target melt-gap at a certain point of time is -3 mm, the target temperature at that point is lowered by -2 degrees, while if the change of the target melt-gap at a certain point is 3 mm, The height can be calibrated to redesign the target temperature profile.

Figure 4 depicts a previous target melt-gap profile and a redesigned current target melt-gap profile, in accordance with an embodiment of the present invention, and Figure 5 illustrates a graph of a target temperature profile draft and a corrected target temperature profile, in accordance with an embodiment of the present invention. .

Referring to FIG. 4, the previous target melt gap was fixed at 0 mm so that the previous target melt gap profile and the redesigned current target melt gap profile change amount can be easily known.

Therefore, the current target melt-gap value redesigned by the data of the previous batch can be understood as the changed amount in the previous target melt-gap. For example, when the length ratio of the single crystal is 0.1, the present target melt gap is 1 mm larger than the previous target melt gap.

Referring to FIG. 5, the draft of the target temperature profile is corrected in accordance with the changed target melt gap. For example, when the length ratio of the single crystal is 0.1, the target melt gap is increased by 1 mm, so the heat loss is expected to increase.

Thus, when the redesign of the target temperature profile is completed over the entire section, the temperature controller 100 controls the heater power with the redesigned target temperature profile to proceed the ingot growing process. (S102)

The melt gap sensor 200 measures the current melt gap in real time and the temperature sensor 70 measures the actual temperature and transmits the measured melt gap to the temperature controller 100. [ (S103)

When the actual temperature is measured to be lower than a desired temperature, the temperature control unit 100 raises the heater power through correction to increase the target temperature. On the contrary, if the actual temperature is measured to be higher than the desired temperature, .

At the same time, the temperature control unit 100 corrects the target temperature in advance even in the event of a difference between the measured melt gap and the target melt gap, in case the actual temperature changes. (S104)

For example, as with redesigning the target temperature profile earlier, if the actual melt-gap measured at a certain point is less than the target melt-gap, the heat loss will be low and correction is required to lower the target temperature. Conversely, If the target melt gap is larger than the target melt gap, the heat loss will be large.

In this embodiment, the actual temperature can be precisely controlled through the feedforward control for predicting the actual temperature change according to the change in the melt gap and controlling the temperature.

Finally, the process proceeds to the corrected target temperature, and the feedforward temperature control of the temperature control section 100 is completed. (S105)

FIG. 6 is a graph showing a comparison example in which the temperature is controlled without considering the change of the melt gap, and a difference between this embodiment in which the temperature is controlled in consideration of the melt gap.

Referring to FIG. 6, the temperature design error of the comparative example is shown in a wide range on the horizontal axis, and the temperature design error of this embodiment is shown in a narrow range on the horizontal axis.

In other words, in the comparative example, the error between the desired temperature and the actual temperature occurred largely throughout the process, and since the embodiment has a small error between the desired temperature and the actual temperature throughout the process, It can be seen that the temperature is controlled.

In other words, in the above-described embodiment, the actual temperature can be precisely controlled by considering the change of the melt gap with the temperature control element, and thereby the diameter of the ingot can be uniformly maintained and the crystal quality can be improved .

10; Chamber 20: Quartz crucible
30: graphite crucible 40: heater
50: heat shield 60: seed chuck
70: Temperature sensor 100: Temperature controller
200: Melt gap sensor 300: ADC sensor
400: Seed lifting part

Claims (6)

A chamber for providing a space necessary for the ingot growing process;
A quartz crucible for holding a silicon melt with a heat resistant container disposed in the chamber;
A heater for heating the quartz crucible;
A seed chuck for fixing a seed for pulling up the ingot from the silicon melt;
A seed upstanding part for immersing the seed chuck in the silicon melt and simultaneously raising the seed chuck;
A heat shield for forming a melt gap with the upper side heat insulating means of the silicon melt;
A diameter sensor for measuring a diameter of an ingot pulled up by the seed lifting portion;
A melt gap sensor for measuring the melt gap;
A temperature sensor for measuring the temperature of the silicon melt; And
And a temperature control unit receiving the actual temperature and the melt gap measured from the temperature sensor and the melt gap sensor,
The temperature controller
Designing a target temperature profile of the current layout in consideration of the target temperature profile of the previous batch measured by the temperature sensor and the actually measured temperature history,
Deriving the difference between the target melt-gap profile of the previous batch and the actual melt-gap measured by the melt-gap sensor,
Wherein the silicon single crystal ingot is grown by redesigning the target temperature profile of the current arrangement through temperature correction according to the difference value of the melt gap. The method according to claim 1,
The temperature control section designs the target temperature profile from data of a previous batch before the process,
Wherein the previous batch data includes a change value of the target melt-gap profile. 3. The method of claim 2,
Wherein the temperature control unit lowers the target temperature at the predetermined time point if the change value of the target melt flow rate at a certain point in time is negative and decreases the target temperature at the certain point in time when the change value of the target melt flow rate at the certain time point is a positive value, And the target temperature profile is designed by increasing the temperature of the ingot. The method according to claim 1,
Wherein the temperature control unit corrects the target temperature profile according to a difference between a target melt gap and an actually measured melt gap. Designing a target temperature profile of the current batch taking into account the measured target temperature profile of the previous batch and the actual measured temperature history;
Deriving the difference between the target melt-gap profile of the previous batch and the actual melt-gap measured;
Redesigning the target temperature profile of the current batch through temperature correction according to the difference value of the melt gap and proceeding the ingot growing process;
Periodically measuring the actual temperature and melt gap of the silicon melt during the process;
Correcting the target temperature profile according to the difference between the measured melt gap and the target melt gap profile;
Proceeding the remaining ingot growth process with the corrected target temperature profile; ≪ / RTI > 6. The method of claim 5,
Controlling the heater power according to a difference between an actual temperature of the silicon melt and a target temperature profile.

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