KR101105475B1 - Method for manufacturing single crystal minimizing process-deviation - Google Patents

Abstract

The present invention discloses a single crystal production method with minimal process variation. In the single crystal manufacturing method of minimizing the process variation according to the present invention, in the single crystal manufacturing method using the Czochralski method to grow a single crystal ingot by gradually pulling the seed to the top while rotating the seed after dipping the melt contained in the quartz crucible, A shouldering process of gradually increasing the diameter of the single crystal to a target diameter by controlling the pulling rate of the seed, and a body process of growing the single crystal to a desired length while maintaining a constant diameter of the single crystal after the shouldering process; In the process, the quartz crucible is rotated at 0.3 to 0.8 rpm in a state where a horizontal magnetic field of 500 G or more is applied to the melt.

According to the present invention, by optimizing the process factors of the shouldering process, the repeatability of the shouldering process can be ensured, and the pulling failure of the single crystal can be minimized. As a result, poor quality of the body portion of the single crystal ingot can be reduced, and the failure of pulling the single crystal can be reduced to shorten the time of the single crystal growth process, thereby improving the productivity of the single crystal.

Czochralski method, monocrystalline ingot, shouldering, horizontal magnetic field

Description

Method for manufacturing single crystal minimizing process-deviation

The present invention relates to a single crystal manufacturing method, and more particularly, to a single crystal manufacturing method capable of minimizing fluctuations in the body process by stabilizing the shouldering process when producing a single crystal using the Czochralski method.

In general, single crystal ingots used as materials for producing electronic components such as semiconductors are manufactured by the Czochralski (hereinafter referred to as CZ) method. In the method for producing a single crystal ingot using the CZ method, a quartz crucible is filled with a solid raw material such as polycrystalline silicon, heated with a heater to be melted to form a melt, and then subjected to a stabilization process. Remove bubbles in the melt. Then, the necking process of dipping the seed, the growth source of the single crystal ingot, on the surface of the melt and pulling the diameter of the growth crystal growing along the seed as small as 3 to 5 mm, Through the shouldering process of controlling the pulling rate to control the vertical and horizontal growth rate of the crystal and extending it to the desired crystal diameter, the body growth process grows to maintain a constant diameter of the single crystal. Let's do it. Then, when the single crystal ingot is grown to a desired length, the tailing process is rapidly rotated to reduce the diameter of the single crystal ingot, and the melt and ingot are separated to complete the production of the single crystal ingot. When the production of the single crystal ingot is completed, the temperature inside the chamber is brought to room temperature, the single crystal ingot is taken out, and the above process is repeated to proceed to the next run of the single crystal ingot manufacturing process.

Of the various single crystal growth processes described above, the shouldering process directly affects the body process. In particular, if there is a deviation in the amount of melt consumed in the shouldering process, the melt gap at the start of the body process is different from the melt gap set as a defect condition, adversely affecting the crystal quality of the early body and the whole body. Here, the melt gap is a distance between the heat shield member disposed around the ingot and the melt surface to shield external emission of heat emitted from the single crystal ingot, and is used as a parameter for controlling the temperature gradient at the solid-liquid interface.

Melt gap control at the beginning of the body process is important because if a melt gap error occurs early in the body process, the melt gap error will accumulate further in the body process later, leading to further deterioration of the single crystal quality in the later body process.

For reference, the melt gap is flawless in the body process. When the crystal gap is released from the melt gap condition, crystal defects (eg, FPDs) resulting from aggregation of point defects due to excessive inflow of point defects such as vacancy and interstitial silicon into single crystals , LPD) occurs in a single crystal. If the pulling speed is the same, the melt gap is intact. If the gap is smaller than the melt gap, the temperature gradient at the liquid-liquid interface increases, which leads to the inflow of excess interstitial silicon into the liquid-liquid interface. If the gap is larger than the gap, the temperature gradient of the solid-liquid interface decreases, causing an excessive amount of vacancy to flow into the solid-liquid interface.

In addition, the melt gap at the beginning of the body process is intact. If the melt gap is out of the condition, the temperature gradient of the solid-liquid interface does not control the single crystal diameter at the beginning of the body process to the desired value or even affects the control of the pulling rate of the single crystal. Done.

On the other hand, as the target diameter of the single crystal increases to 300 mm or more, the amount of melt contained in the crucible is increasing. In the shouldering process, the quartz crucible is rotated to control the convection of the melt. In the production of a single crystal having a diameter of 300 mm or more, the quartz crucible is rotated at a high speed of 3 rpm or more to control the convection of the melt.

In the process of growing single crystals, the inner wall of the quartz crucible reacts with the melt and silica, which constitutes the quartz crucible, to produce crystalline precipitates.As the rotation speed of the quartz crucible increases, the formation rate of the crystalline precipitates is increased faster and the quartz crucible is Softening is further promoted. As a result, the crystalline precipitates are separated from the inner wall of the quartz crucible, move to the solid-liquid interface through the convection of the melt, and then flow into the single crystal through the solid-liquid interface to act as a cause of dielectric dislocation. In addition, when the quartz crucible is rotated at high speed, the amount of oxygen eluted from the quartz crucible increases, so that it is difficult to properly control the oxygen concentration flowing into the single crystal to the level required by the customer.

Therefore, in order to improve the quality and yield of the single crystal by stably performing the body process, it is necessary to precisely control the melt consumption in the shouldering process that is run to run to minimize melt gap error at the beginning of the body process. have. In addition, it is important to introduce other technical means capable of controlling the convection of the melt to lower the rotational speed of the quartz crucible, thereby suppressing the separation of crystalline precipitates and at the same time ensuring the ease of controlling the oxygen concentration.

The present invention was devised to solve the above problems, and by optimizing the process factors of the shouldering process, it is possible to secure the repeatability of the shouldering process, and to minimize the process variation that can prevent deterioration of single crystal quality. Its purpose is to provide a single crystal manufacturing method.

In order to achieve the above technical problem, a single crystal manufacturing method of minimizing process variation according to the present invention comprises a Czochralski method of growing a single crystal ingot by slowly raising the seed while dipping the seed in a melt contained in a quartz crucible and rotating the seed. In the single crystal manufacturing method used, a shouldering step of gradually increasing the diameter of the single crystal to the target diameter by controlling the pulling rate of the seed, and a body for growing the single crystal to a desired length while maintaining a constant diameter of the single crystal after the shouldering process And a step of rotating the quartz crucible at 0.3 to 0.8 rpm while applying a horizontal magnetic field of 500 G or more to the melt.

Preferably, the horizontal magnetic field is 500 to 1200 G, and the position of the maximum gauge plane (MGP) is located at a point -135 to -35 mm downward from the melt surface.

Preferably, after entering the body process, the horizontal magnetic field is increased and applied to 2500 G or more.

According to the present invention, by optimizing the process factors of the shouldering process, the repeatability of the shouldering process can be ensured, and the pulling failure of the single crystal can be minimized. As a result, poor quality of the body portion of the single crystal ingot can be reduced, and the failure of pulling the single crystal can be reduced to shorten the time of the single crystal growth process, thereby improving the productivity of the single crystal.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. Prior to this, words used in this specification and claims are not to be construed as limiting in their usual or dictionary sense, but rather to properly define the concept of terms in order to best describe the inventor's own invention in the best way possible. It should be interpreted as meaning and concept corresponding to the technical idea of the present invention based on the principle that it can. Therefore, the embodiments described in the specification and the drawings shown in the drawings are only the most preferred embodiment of the present invention and do not represent all of the technical idea of the present invention, various modifications that can be replaced at the time of the present application It should be understood that there may be equivalents and variations.

1 is a schematic configuration diagram of a single crystal manufacturing apparatus used for the practice of the single crystal manufacturing method minimized the process variation in accordance with a preferred embodiment of the present invention.

Referring to FIG. 1, the single crystal manufacturing apparatus includes a quartz crucible 10 in which a molten material M in which a solid raw material such as polycrystalline silicon is melted at a high temperature is accommodated, and a quartz crucible 10 wrapped around an outer circumferential surface of the quartz crucible 10. ) Crucible housing 20 to support a certain form, the crucible rotation is installed at the bottom of the crucible housing 20 to rotate the quartz crucible 10 together with the housing 20 to raise or lower the quartz crucible 10. Means 30, a heater 40 for heating the quartz crucible 10 spaced apart from the side wall of the crucible housing 20, the heat generated from the heater 40 is installed outside the heater 40 A single crystal is pulled while rotating the single crystal ingot (IG) in a predetermined direction from the melt (M) accommodated in the quartz crucible 10 by using a heat insulating means 50 and a seed crystal seed to prevent the outflow to the outside. Lifting means (60), The heat shield means 70 for shielding the external emission of heat emitted to the ingot IG for forming the temperature gradient of the liquid interface and forming a melt gap with the melt M, the melt M along the outer circumferential surface of the single crystal ingot IG. Inert gas supply means (not shown) for supplying an inert gas (eg, Ar gas) to the upper surface of the () and magnetic field applying means 80 for applying a horizontal magnetic field to the quartz crucible 10. Here, the horizontal magnetic field refers to a magnetic field in which the direction of the magnetic field near the MGP (Max Gauss Plane) having the greatest magnetic field is almost horizontal and the upper and lower magnetic fields have a Gaussian distribution based on the MGP.

Since the above components are typical components of the single crystal manufacturing apparatus using the CZ method, which is well known in the art, detailed description of each component will be omitted.

In the embodiment of the present invention, the melt (M) is a solid raw material such as polycrystalline silicon and impurities are laminated on the quartz crucible 10 and melted using heat radiated from the heater 40. However, since the present invention is not limited to the type of the melt M, the type and composition of the melt M vary depending on the type of the semiconductor single crystal grown by the CZ method.

In the single crystal production method according to a preferred embodiment of the present invention, first, the solid raw material filled in the quartz crucible 10 is melted to form a melt M. When the melt M is formed, the melt M contained in the quartz crucible 10 is controlled by controlling the magnetic field applying means 80 while rotating the quartz crucible 10 in a predetermined direction by using the crucible rotating means 30. ) Apply a horizontal magnetic field of 500 G or more. Preferably, the horizontal magnetic field is applied at an intensity of 500 to 1200 G. The strength condition of the horizontal magnetic field is chosen for the purpose of stabilizing the convection of the melt surface. On the other hand, the MGP of the horizontal magnetic field is preferably located in the MGP point -135mm to -35mm relative to the melt surface. The position condition of the MGP is approximately coincident with the region where the temperature rises the highest by the heat generated from the heater 40 among the sidewalls of the quartz crucible 10. Therefore, the hot melt of the crucible side wall adjacent to the heater can suppress the natural convection by the magnetic field to stabilize the convection of the melt surface. Then, the single crystal pulling means 60 is controlled to dip the seed into the melt M to form a necking portion which is pulled down to about 3 to 5 mm in diameter. Subsequently, a shouldering process is performed to control the pulling rate of the single crystal to control the vertical growth rate and the horizontal growth rate of the crystal to extend to the desired crystal diameter.

In the shouldering process according to the present invention, while maintaining the horizontal magnetic field applied under the above conditions, by controlling the crucible rotating means 30, the shoulder portion while rotating the quartz crucible 10 in the speed range of 0.3 ~ 0.8rpm Proceed with formation. When the shouldering process proceeds under these conditions, the convection of the melt can be stabilized, thereby minimizing the process variation due to the thermal environment change in the chamber. At this time, if the crucible rotation speed is less than 0.3rpm, the rotational force of the melt is too small, there is a problem that the melt does not mix well. On the other hand, if the crucible rotation speed is 0.8rpm or more, the influence of the heater power is increased to promote deterioration of the crucible inner wall. When the diameter of the single crystal ingot IG is increased to a desired size in the shouldering process, the body growth process is switched.

After entering the body growth process, the magnetic field applying means is controlled to increase the strength of the horizontal magnetic field to 2500 G or more. Then, the amount of heat flow from the heater 40 toward the solid-liquid interface side is further increased so that heat transferred by the heat flow from the heater 40 is smoothly transferred to the solid-liquid interface side. Accordingly, the temperature gradient of the solid-liquid interface, in particular, the temperature gradient of the solid-liquid interface center is increased, so that the pulling speed of body portion growth can be improved.

After the growth of the body part is completed, the growth rate of the single crystal ingot IG is completed by releasing the lower end of the ingot IG from the melt M while gradually decreasing the diameter of the ingot IG by gradually increasing the pulling speed. do.

Hereinafter, the present invention will be described in more detail with reference to experimental examples. The following experimental examples are described for the purpose of helping the understanding of the present invention, and the present invention should not be construed to limit the present invention to terms or experimental conditions described in the experimental examples.

< Experimental Example >

One. Magnet  century

(One). Melt  Temperature Scatter

Charge 400 kg of polycrystalline silicon in a quartz crucible and melt it using a heater, then increase the horizontal magnetic field at -135 mm below the melt surface in steps of 0 to 4000 G (the magnetic field strength at MGP). Spot temperature was measured twice over time using two-color parameters installed on top of the growth chamber. Here, the temperature measurement method using the two-color parameter is to measure the temperature of the melt surface using the two-color parameter installed on the chamber. The standard deviation of the melt surface temperature for each of the magnetic fields applied at 0 G, 400 G, 800 G, 1000 G, 2000 G, 3000 G, and 4000 G was calculated, and the results are shown in FIG. ) And Table (b).

Referring to FIG. 2, the dispersion of the melt surface temperature is 55.8 at 0 G, 35.4 at 400 G, 25.4 at 800 G, 24 at 1000 G, and 23.6 at 2000 G. , 20.5 at 3000 G and 17.5 at 4000 G. As a result, it can be seen that when the intensity of the magnetic field is more than 800G, the dispersion of the melt surface temperature drops to 25.4 or less, which is relatively stable.

(2). Shoulder  Defective rate

400 kg of polycrystalline silicon was charged into the quartz crucible and melted using a heater, and then the horizontal magnetic fields were 0 G, 500 G, 800 G, 1000 G, 1500 G, respectively, with the quartz crucible fixed at a rotational speed of 0.5 rpm. Each shouldering process was repeated 10 times under conditions applied at 2500 G (which is the magnetic field strength in MGP). In the shouldering process, the diameter of the single crystal was increased to 300 mm. The shoulder failure rate was calculated by calculating the ratio of the number of failures to the number of attempts of each shouldering process when the strength of the magnetic field was applied at 0 G, 500 G, 800 G, 1000 G, 1300 G, and 2500 G. As a result, 3 is a graph (a) and a table (b).

Referring to FIG. 3, the shoulder failure rate according to the strength of the applied horizontal magnetic field is 400% when the strength of the magnetic field is 0 G, 20% when 500 G, 0% when 800 G, and 0 when 1000 G. %, 20% at 1200 G, 50% at 1500 G, and 100% at 2500 G. As a result of the experiment, it can be seen that when the strength of the magnetic field is 500 G to 1200 G, the optimum value of the shoulder failure rate is 20% or less.

2. Crucible Rotation

(One). Heater power Scatter

400 kg of polycrystalline silicon was charged into the quartz crucible and melted using a heater, and the horizontal magnetic field was fixed at 2500 G (magnetic field strength in MGP) at -135 mm below the melt surface, and the rotation speed of the quartz crucible was 0.1. Heater power applied to the melt was measured several times at regular time intervals, increasing stepwise to ˜8.0 rpm. The power of the heater changes automatically according to the temperature of the melt surface by feedback control. It decreases as the melt surface temperature decreases and decreases as the melt surface temperature increases. Standard deviations of the heater powers at the rotational speeds of the quartz crucible at 0.1 rpm, 0.3 rpm, 0.5 rpm, 0.8 rpm, 1.5 rpm, 2.0 rpm, 4.0 rpm and 8.0 rpm were calculated and the results are shown in the graph of FIG. (a) and (b) are shown.

Referring to Figure 4, the dispersion of the heater power for heating the quartz crucible is 3.84 when the rotation speed of the quartz crucible is 0.1rpm, 2.35 at 0.3rpm, 2.21 at 0.5rpm, 2.13 at 0.8rpm, It was 2.4 at 1.5 rpm, 2.6 at 2.0 rpm, 2.9 at 4.0 rpm and 4.2 at 8.0 rpm. As a result, it can be seen that when the rotation speed of the quartz crucible is 0.3 ~ 0.8rpm, the distribution of heater power is the least 2.1 ~ 2.5, and when the 0.1 and 8.0rpm, the dispersion of the heater power is larger than 3.8.

(2). Shoulder  Defective rate

After charging 400kg of polycrystalline silicon in the quartz crucible and melting it using a heater, the rotation speed of the quartz crucible was fixed while the horizontal magnetic field was fixed at 2500 G (the magnetic field strength in the MGP) at -135 mm below the melt surface. The shoulder failure rate was calculated by calculating the ratio of the number of failures to the number of attempts of each shouldering process when rotating at 0.1 rpm, 0.3 rpm, 0.5 rpm, 0.8 rpm, 1.5 rpm, 2.0 rpm, and 8.0 rpm, respectively. 5 is a graph (a) and a table (b).

Referring to Figure 5, the shoulder failure rate according to the rotation speed of the quartz crucible is 100% when the crucible rotation speed is 0.1 rpm, 20% at 0.3 rpm, 0% at 0.5 rpm, 20% at 0.8 rpm 35% at 1.5 rpm, 40% at 2.0 rpm and 40% at 8.0 rpm. As a result of the experiment, when the rotation speed of the quartz crucible is 0.3 rpm ~ 0.8 rpm, it can be seen that the optimal value appears as the shoulder failure rate is 20% or less.

< Example >

Comparative Example 1

400 kg of polycrystalline silicon was charged in a quartz crucible and melted using a heater, and then a single crystal ingot having a body diameter of 300 mm was grown. At this time, the shouldering process was performed by setting the horizontal magnetic field to 0 G and the quartz crucible rotation speed to 8 rpm, and the single crystal growth process was repeated five times.

Comparative Example 2

400 kg of polycrystalline silicon was charged in a quartz crucible and melted using a heater, and then a single crystal ingot having a body diameter of 300 mm was grown. At this time, the shouldering process was performed by setting the horizontal magnetic field to 2500G and the quartz crucible rotation speed to 0.1 rpm, and the single crystal growth process was repeated five times. The 2500 G was the magnetic field strength at the MGP, where the MGP was located -135 mm below the melt surface.

Example 1

400 kg of polycrystalline silicon was charged in a quartz crucible and melted using a heater, and then a single crystal ingot having a body diameter of 300 mm was grown. At this time, the shouldering process was performed by setting the horizontal magnetic field to 800 G and the quartz crucible rotation speed to 0.8 rpm, and the single crystal growth process was repeated five times. The 800 G was the magnetic field strength at the MGP, where the MGP was located -135 mm below the melt surface.

Example 2

400 kg of polycrystalline silicon was charged in a quartz crucible and melted using a heater, and then a single crystal ingot having a body diameter of 300 mm was grown. At this time, the shouldering process was performed by setting the horizontal magnetic field to 1000G and the quartz crucible rotation speed to 0.5 rpm, and the single crystal growth process was repeated five times. The 1000 G was the magnetic field strength at the MGP, where the MGP was located -135 mm below the melt surface.

In Comparative Examples 1-2 and Examples 1-2, the shoulder failure rate, the shoulder length distribution value, and the defect occurrence rate were calculated.

The shoulder failure rate was calculated by calculating the ratio of the number of failures to the number of attempts of the shouldering process. The case where the shouldering process fails is a case where structure loss occurs in the shouldering process. The shoulder length distribution value was calculated by measuring the length of the shoulder grown for each run and calculating the standard deviation of the length. In addition, the defect incidence rate was calculated by measuring the total body length in which defects were generated compared to the body length of the entire single crystal and calculating the ratio thereof. Decision defects considered in calculating the defect incidence rate are FPD (Flow Pattern Defect), Large Dislocation Loop (LDP), and Direct Surface Oxide Defect (DSOD). The measurement results for Examples and Comparative Examples are summarized in Table 1 below.

MS (gauss) C / R (rpm) Shoulder length spread (mm) Defective Rate (%) Shoulder failure rate (%) Comparative Example 1 0 8 7.25 3.0 40 Comparative Example 2 2500 0.1 6.4 2.5 100 Example 1 800 0.8 5.2 2.0 20 Example 2 1000 0.5 4.26 1.4 0

Referring to Table 1, Comparative Example 1 has a shoulder length dispersion value of 7.25mm, a defect occurrence rate of 3.0%, a shoulder failure rate of 40%, it can be seen that the quality of the single crystal is not good and the shoulder failure rate is also large. In Comparative Example 2, the shoulder length distribution value was 6.4mm, the defect occurrence rate was 2.5%, and the shoulder failure rate was 100%, and the shoulder length dispersion value and the defect occurrence rate were slightly improved compared to Comparative Example 1, but the shoulder failure rate was very high It can be seen that the stability of the process is very low.

On the other hand, Example 1 shows that the shoulder length dispersion value is 5.2 mm, the defect occurrence rate is 2.0%, and the shoulder failure rate is 20%, and that the quality of single crystal is better and the shoulder failure rate is also significantly lower than that of Comparative Examples 1-2. Can be. In Example 2, the shoulder length dispersion value was 4.26, the defect occurrence rate was 1.4%, and the shoulder failure rate was 0%. Thus, it was found that the quality of the single crystal was very excellent as compared with Comparative Examples 1 and 2, and no shoulder failure occurred. .

According to the experimental results as described above, when the single crystal is manufactured by the single crystal manufacturing method according to the present invention, since the shoulder length scattering value is reduced, the melt consumption variation in the shouldering process can be reduced. This ensures repeated reproducibility of the shouldering process, thereby reducing the melt gap error at the beginning of the body process. The reduced melt gap error facilitates the control of diameter and pull rate early in the body process. In addition, the temperature gradient control of the solid-liquid interface can be more stabilized to stabilize the process throughout the body to produce high quality single crystals free of defects.

As described above, although the present invention has been described by way of limited embodiments and drawings, the present invention is not limited thereto and is intended by those skilled in the art to which the present invention pertains. Of course, various modifications and variations are possible within the scope of equivalents of the claims to be described.

The following drawings, which are attached to this specification, illustrate preferred embodiments of the present invention, and together with the detailed description of the present invention serve to further understand the technical idea of the present invention, the present invention includes the matters described in such drawings. It should not be construed as limited to.

1 is a schematic configuration diagram of a single crystal manufacturing apparatus used for the practice of the single crystal manufacturing method minimized the process variation in accordance with a preferred embodiment of the present invention.

2 is a view showing the results of calculating the standard deviation of the melt surface temperature in the experimental example.

3 is a view showing a result of calculating the shoulder failure rate according to the strength of the horizontal magnetic field in the experimental example.

4 is a view showing a result of calculating the standard deviation of the heater power for heating the quartz crucible in the experimental example.

5 is a view showing a result of calculating the shoulder failure rate according to the rotational speed of the quartz crucible in the experimental example.

Claims (4)

In the single crystal manufacturing method using the Czochralski method of growing a single crystal ingot by dipping the seed into the melt contained in the quartz crucible and gradually pulling it upward while rotating the seed, It includes a shouldering process of controlling the pulling rate of the seed to gradually increase the diameter of the single crystal to the target diameter and a body process of growing the single crystal to a desired length while maintaining a constant diameter of the single crystal after the shouldering process, In the shouldering step, the quartz crucible is rotated at 0.3 ~ 0.8rpm in a state in which a horizontal magnetic field of 500 G or more is applied to the melt. The method of claim 1, The horizontal magnetic field is a single crystal manufacturing method, characterized in that 500 to 1200G. 3. The method of claim 2, The horizontal magnetic field is a single crystal manufacturing method characterized in that the position of the MGP (Max Gauss Plane) is located at the point -135 ~ -35mm downward from the melt surface. The method of claim 1, After entering the body process, the horizontal magnetic field is increased by 2500 G or more, characterized in that for applying a single crystal.

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