TWI613334B - Automatic crystal growth method with high success rate - Google Patents

Abstract

An automatic crystal growth method for improving the success rate of crystal growth includes the following steps. The temperature of a liquid surface of a molten soup in a crucible is adjusted to reach a preset target temperature. Next, a seed crystal was used to contact the liquid surface of the molten soup in the crucible. Then, pre-pulling is performed to move the seed crystal upward at a set speed to leave the liquid surface, and at the same time, monitor a diameter of a pre-pulling section formed between the seed crystal and the liquid surface at the liquid surface. When the diameter is greater than a preset diameter, the temperature of the molten soup is increased. When the diameter is smaller than the preset diameter, lower the temperature of the molten soup. When the diameter of the pre-stretching section at the liquid surface is maintained at the preset diameter, a neck, a shoulder, and a body are formed under the pre-stretching section according to the crystal growth procedure.

Description

Automatic crystal growth method for improving crystal growth success rate

The invention relates to a method for growing crystals.

In recent years, the semiconductor industry has been booming, and silicon wafers are the most basic necessities of the semiconductor industry. The growth methods of silicon wafers include the Floating Zone Method, Laser Heated Pedestal Growth, and Czochralski Method (CZ method for short). Among them, the Chai's growth method has better economic benefits, so it has become the main growth method for large-size wafers. The control of the temperature of the silicon melt-especially the surface temperature of the liquid silicon soup is extremely important, and its temperature will have a great influence on the quality of the crystal growth and the success rate of the crystal growth. However, the thermal field in the general crystal growth furnace will continue to change due to the increase of use time, which will cause the liquid surface temperature to change every time. The general temperature measurement methods include thermocouple measurement and infrared measurement. Wen Yi and so on. However, due to the accuracy of the instrument in the furnace environment, the initial fine-tuning mostly relies on artificial or setting an empirical value to control the heater output power to achieve a preliminary suitable crystal growth temperature.

In the growth of single crystal of the CZ method, in a chamber maintained under an inert gas atmosphere under reduced pressure, seed crystals are immersed in the raw materials of silicon accumulated in a crucible In the soup. When the operator judges that the size of the bright spot generated by the contact between the seed crystal and the molten soup reaches the empirical value, the crystal growing device is operated to slowly pull the impregnated seed crystal to sequentially grow a single crystal silicon rod under the seed crystal Neck, shoulders and body. In fact, the size of the bright spot produced by the contact between the seed crystal and the molten soup is to a certain extent positively related to the temperature of the molten soup, so this will be used as the basis for judging whether it is possible to start pulling the seed crystal.

However, such judgment is left to the operator to make judgment based on personal experience, which will lead to a large difference in the initial temperature of each crystal growth, and it is easy to produce fractures when forming the neck or poor removal of lattice defects, resulting in crystals The crystallization rate is poor. Moreover, when the operator is replaced, there is also the problem of different subjective standards for each person, resulting in a difference in initial temperature, and finally the quality of the grown crystal is different. At present, another way to judge whether it is possible to start pulling the seed crystal is to use a high-temperature temperature measurement to measure the temperature of the molten soup. However, due to the space limitation of the crystal growth device, the high temperature thermometer cannot measure the temperature of the area where the melt actually contacts the seed crystal, but only the energy can measure the temperature of the nearby area, and there are still error values. Therefore, how to accurately determine the timing of starting to pull the seed crystal to improve the crystal crystallization rate and the consistency of the crystal quality has become a subject worth studying.

The invention provides a method for growing crystals, which can solve the problems of poor crystallization rate and quality consistency of crystals in the conventional technology.

The automatic crystal growth method for improving the success rate of crystal growth of the present invention includes the following steps. The temperature of a liquid surface of a molten soup in a crucible is adjusted to reach a preset target temperature. Next, a seed crystal was used to contact the liquid surface of the molten soup in the crucible. Then, pre-pulling is performed to move the seed crystal upward at a set speed to leave the liquid surface, and at the same time, monitor a diameter of a pre-pulling section formed between the seed crystal and the liquid surface at the liquid surface. When the diameter is greater than a preset diameter, the temperature of the molten soup is increased. When the diameter is smaller than the preset diameter, lower the temperature of the molten soup. When the diameter of the pre-stretching section at the liquid surface is maintained at the preset diameter, a neck, a shoulder, and a body are formed under the pre-stretching section according to the crystal growth procedure.

In an embodiment of the invention, the preset diameter is 10 mm.

In an embodiment of the invention, the diameter is the diameter of the pre-stretching section at a height of 26 mm from the liquid level.

In an embodiment of the invention, the diameter is measured by image capture.

In an embodiment of the invention, the method of growing crystals further includes measuring the temperature of the liquid surface with a pyrometer (Pyrometer) to reach a preset temperature before contacting the seed crystal with the liquid surface.

In an embodiment of the invention, the preset temperature is 1450 ° C.

In an embodiment of the present invention, the difference between the diameter and the preset diameter is proportional to the adjustment value of the temperature of the molten soup.

In an embodiment of the invention, the seed crystal is a single seed crystal.

In an embodiment of the invention, the method for determining the relationship between the diameter and the preset diameter is automatically determined by the computer.

Based on the above, in the crystal growth method of the present invention, whether the temperature needs to be increased or decreased by the diameter of the pre-stretched segment is used to obtain a uniform timing for forming the neck, thereby improving the crystal crystallization rate and the consistency of the crystal quality .

In order to make the above-mentioned features and advantages of the present invention more obvious and understandable, the embodiments are specifically described below and described in detail in conjunction with the accompanying drawings.

FIG. 1 is a flowchart of a method for growing crystals according to an embodiment of the invention. 2A to 2D are schematic cross-sectional views of a method of growing crystals according to an embodiment of the invention. Please refer to FIGS. 1 and 2A. In the automatic crystal growth method of this embodiment that does not require human intervention and can improve the success rate of the crystal growth, the equipment for performing the automatic crystal growth method includes, for example, a basic crystal growth system, An infrared thermometer, a high-resolution optical measurement system and a software that can control the crystal rise speed (diameter control loop) and the melting temperature (temperature control loop).

First, the temperature of a liquid surface 72 of a molten soup 70 in a crucible 60 is adjusted to reach a preset target temperature, which is step S120. The adjustment of the temperature of the liquid surface 72 is achieved, for example, by performing the temperature control loop using the aforementioned software. Next, a seed crystal 50 is brought into contact with the liquid surface 72 of the molten soup 70 in the crucible 60, which is step S130. In addition, before step S120 is performed, the temperature of the liquid surface 72 may be selectively measured with the pyrometer 80, so as to set the power and time required for adjusting the temperature. This is step S110. For example, the seed crystal 50 may be a single seed crystal, but in other embodiments, the seed crystal may also be a poly seed crystal or other seed crystals. The molten soup 70 in the crucible 60 is made of a semiconductor material such as polycrystalline silicon and a dopant such as boron and phosphorus is melted into a liquid at a high temperature, but the present invention is not limited to the material of the molten soup 70. After putting the material used to form the molten soup 70 into the crucible 60, a heater (not shown) can be set to heat the crucible 60 at a power of, for example, 80 KW, and the target temperature of the heater is set at, for example, 1250 ° C to Between 1350 ° C. Then, the automatic control loop of the melting temperature is turned on, and the temperature of the liquid surface 72 measured by the pyrometer 80 reaches a preset target temperature of, for example, 1450 ° C, and then the seed crystal 50 hung on the suspension wire 40 is lowered to contact The position of the liquid level 72. The pyrometer 80 may be an infrared thermometer or other pyrometer.

Next, please refer to FIGS. 1 and 2B. Unlike the conventional technique, after the seed crystal 50 contacts the liquid surface 72, the seed crystal 50 starts to be raised to form a neck. The method of growing crystal in this embodiment is followed by an automatic Temperature control loop control (pre-stretching), so that the seed crystal 50 moves up at a set speed away from the liquid surface 72 to form a pre-stretching segment 110 between the seed crystal 50 and the liquid surface 72, and for example A high-resolution optical image measuring system is used to monitor a diameter D10 of the pre-stretching section 110 at the liquid surface 72. This is step S140. When the diameter D10 is greater than a preset diameter, it means that the temperature of the molten soup 70 is lower than the ideal temperature, so the temperature of the molten soup 70 needs to be increased, and this temperature increase can be automatically performed by the temperature control loop software control device. When the diameter D10 is smaller than the preset diameter, it means that the temperature of the molten soup 70 is higher than the ideal temperature, so the temperature of the molten soup 70 needs to be lowered, and this temperature-lowering action can be automatically performed by the temperature control loop software control device.

For example, the preset diameter may be 10 mm. When the diameter D10 of the pre-stretching section 110 at the liquid surface 72 is monitored to be 8.1 mm, it means that the temperature of the liquid surface 72 beside the seed crystal 50 is higher than the ideal temperature, and the temperature of the heater is about 6 ° C higher, so it must be adjusted Set the heater temperature or use other methods to reduce the heater temperature by 6 ° C. When the diameter D10 of the pre-stretching section 110 at the liquid surface 72 is 11.3 mm, it means that the temperature of the liquid surface 72 next to the seed crystal 50 is lower than the ideal temperature, and the heater temperature is about 4 ° C higher, so it must be adjusted The heater's set temperature or other methods are used to increase the heater's temperature by 4 ° C. When the diameter D10 of the pre-stretching section 110 at the liquid surface 72 is 14.5 mm, it means that the temperature of the liquid surface 72 beside the seed crystal 50 is lower than the ideal temperature, and the temperature of the heater is about 14 ° C lower, so it must be adjusted The heater's set temperature or other methods are used to increase the heater's temperature by 14 ° C. When the diameter D10 of the pre-stretching section 110 at the liquid surface 72 is 17.3 mm, it means that the temperature of the liquid surface 72 next to the seed crystal 50 is lower than the ideal temperature, and the temperature of the heater is about 24 ° C lower, so it must be adjusted The heater's set temperature or other methods are used to increase the heater's temperature by 24 ° C. When the diameter D10 of the pre-stretching section 110 at the liquid surface 72 is 21.5 mm, it means that the temperature of the liquid surface 72 next to the seed crystal 50 is lower than the ideal temperature, and the temperature of the heater is about 34 ° C lower, so it must be adjusted The heater's set temperature or other methods are used to increase the heater's temperature by 34 ° C. In this embodiment, the difference between the diameter D10 of the pre-stretching section 110 at the liquid surface 72 and the preset diameter is proportional to the adjustment value of the temperature of the molten soup 70. In other words, as long as the diameter D10 of the pre-stretching section 110 at the liquid surface 72 is monitored, the temperature of the molten soup 70 can be known approximately. The experimental parameters for obtaining the above values include: the diameter of the body of the formed ingot is 6 inches; the lattice direction of the formed single crystal silicon is 100; the dopant of the molten soup 70 is boron; and the diameter of the crucible 60 is 18 inches.

In this embodiment, the diameter D10 is, for example, the diameter of the pre-stretching section 110 at a height of 26 mm from the liquid surface 72. The method of monitoring to obtain the diameter D10 is, for example, the image capture method, that is, using the CCD or other components to obtain the image of the pre-stretching section 110 at the liquid surface 72, and the computer software interprets the image to obtain the diameter D10 Value. In addition, the method for determining the relationship between the diameter D10 and the preset diameter is, for example, automatically determined by a computer, thereby avoiding artificial subjective judgment errors. When the computer automatically determines that the diameter D10 is larger or smaller than the preset diameter, it can automatically adjust the heater heating power accordingly, and the adjustment amount can be pre-loaded in the database of the computer.

When monitoring confirms that the diameter D10 of the pre-stretching section 110 at the liquid surface 72 remains at the preset diameter, the device will automatically perform the next stage of action, that is, forming a neck under the pre-stretching section 110 according to the crystal growth process 120. A shoulder 130 and a body 140. This is step S150. In addition, a tail 150 may be formed under the body 140. According to the above, the difference between the ingot formed by the growth method of this embodiment and the ingot formed by the conventional technique is that the ingot formed by the growth method of this embodiment is between the seed 50 and the neck There is also a pre-tension section 110 between 120. In most cases, the diameter of the pre-stretching section 110 changes little in the length direction, and the diameter of the pre-stretching section 110 is much larger than the diameter of the neck 120. Since the crystal growth method of this embodiment includes the formation of the pre-stretching section 110, the temperature of the liquid surface 72 at the junction of the molten soup 70 and the pre-stretching section 110 can be accurately grasped by monitoring the diameter of the pre-stretching section 110, and During each crystal growth process, the temperature of the liquid surface 72 at the time when the neck 120 starts to form is controlled to be consistent. In this way, not only can the success rate when forming the neck 120 be improved, but also the crystallization rate of the entire ingot can be increased, and the initiation temperature when each ingot is formed is the same, and the ingot with consistent quality can be obtained, not It is affected by the human judgment error of the operator. The parameters when forming the neck 120 are, for example: the rotation speed of the seed crystal 50 is 14 rpm; the rotation speed of the crucible 60 is -8 rpm; the growth speed of the neck 120 is 200 mm / hr; the diameter of the neck 120 is 6 mm; The length of the neck is 200 mm.

In summary, in the method for growing crystals of the present invention, the pre-stretching step is performed before forming the neck, so the timing of starting the neck formation can be accurately judged from the diameter of the pre-stretching section, thereby improving the crystal crystallization rate and Consistency of crystal quality.

In addition, the crystal growth method of the present invention is a combination of automatic melt temperature control and automatic pre-pull adjustment, which can achieve an automatic crystal growth method without artificial judgment and temperature adjustment, and has a high success rate and stability of seeding.

Although the present invention has been disclosed as above with examples, it is not intended to limit the present invention. Any person with ordinary knowledge in the technical field can make some changes and modifications without departing from the spirit and scope of the present invention. The scope of protection of the present invention shall be subject to the scope defined in the appended patent application.

S110 ~ S150‧‧‧Step
40‧‧‧Suspended wire
50‧‧‧ Seed
60‧‧‧Crucible
70‧‧‧Melting soup
72‧‧‧Liquid
80‧‧‧ pyrometer
110‧‧‧Pre-stretch
120‧‧‧ Neck
130‧‧‧Shoulder
140‧‧‧Body
150‧‧‧tail
D10‧‧‧Diameter

FIG. 1 is a flowchart of a method for growing crystals according to an embodiment of the invention. 2A to 2D are schematic cross-sectional views of a method of growing crystals according to an embodiment of the invention.

S110 ~ S150‧‧‧Step

Claims (8)

A method for growing crystals, comprising: adjusting the temperature of a liquid surface of a molten soup in a crucible to reach a preset target temperature; using a seed crystal to contact the liquid surface of the molten soup in the crucible; performing pre-drawing, The seed crystal is moved upward at a set speed to leave the liquid surface, while monitoring a diameter of a pre-stretched section formed between the seed crystal and the liquid surface at the liquid surface, when the diameter is greater than a pre When the diameter is set, the temperature of the molten soup is increased, and when the diameter is smaller than the preset diameter, the temperature of the molten soup is lowered; and when the diameter of the pre-stretching section at the liquid surface is maintained at the preset diameter, the A neck, a shoulder and a body are formed under the pre-stretching section according to the crystal growth procedure, wherein the diameter of the pre-stretching section is larger than the diameter of the neck. The crystal growth method as described in item 1 of the patent application scope, wherein the preset diameter is 10 mm. The crystal growth method as described in item 1 of the patent application, wherein the diameter is measured by image capture. The method of growing crystals as described in item 1 of the patent application scope further includes measuring the temperature of the liquid surface with a pyrometer to reach a preset temperature before bringing the seed crystal into contact with the liquid surface. The crystal growth method as described in item 4 of the patent application range, wherein the preset temperature is 1450 ° C. The crystal growth method as described in item 1 of the patent application range, wherein the difference between the diameter and the preset diameter is proportional to the adjustment value of the temperature of the molten soup. The method of growing crystals as described in item 1 of the patent application, wherein the seed crystal is a single crystal seed. The crystal growth method as described in item 1 of the patent application scope, wherein the method for determining the relationship between the diameter and the preset diameter is automatically determined by a computer.