KR102748193B1 - Method for growing silicone single crystal - Google Patents

Abstract

The invention provides a method for growing a silicon single crystal, comprising: a step of first dipping a seed by lowering it from above a silicon melt; and a step of second dipping the seed in the direction of the silicon melt; wherein good dipping of the first dipping is determined by measuring the brightness of a meniscus shape, and good dipping of the second dipping is determined by confirming a mark displayed at a certain height of the seed.

Description

{METHOD FOR GROWING SILICONE SINGLE CRYSTAL}

The invention relates to a method for growing a silicon single crystal, and more specifically, to a method for accurately determining whether a seed is well-dipped when dipping it in a silicon melt and then performing a necking process to grow a high-quality silicon single crystal.

A typical silicon wafer is made by a process including a single crystal growth process to create a single crystal (ingot), a cutting process to cut the single crystal (slicing) to obtain a thin, disc-shaped wafer, a grinding process to remove any mechanical damage remaining on the wafer due to the cutting process, a polishing process to harden the wafer, and a cleaning process to harden the polished wafer and remove any abrasive or foreign substances attached to the wafer.

Among the processes described above, the process of growing a silicon single crystal can be performed by placing polycrystalline raw materials into a crucible and melting them to produce a silicon melt (Si melt), dipping a seed (seed crystal) into the silicon melt, and growing and raising a silicon single crystal therefrom.

Silicon single crystals grow sequentially from the seed into the neck, shoulder, and body, and then finish growing into the tail.

After dipping the seed into the silicon melt while rotating, when the temperature of the silicon melt is within a certain range, it is judged as good dipping, and then the seed crystal is pulled up to grow the silicon single crystal ingot. Judging good dipping is important in the growth of the silicon single crystal ingot, and if the seed is dipped before sufficient preheating, icing may occur on the surface of the silicon melt due to the thermal shock between the cold seed and the high-temperature silicon melt.

The occurrence of icing or other failures in good dipping can result in quality degradation, such as the occurrence of crystal defects in the growing silicon single crystal. In addition, it is difficult to accurately determine whether good dipping has occurred with the naked eye from outside the chamber.

The present invention is intended to solve the above-described problems and to provide a method for dipping a seed in a silicon melt and determining the same for growing a silicon single crystal.

The invention provides a method for growing a silicon single crystal, comprising: a step of first dipping a seed by lowering it from above a silicon melt; and a step of second dipping the seed in the direction of the silicon melt; wherein good dipping of the first dipping is determined by measuring the brightness of a meniscus shape, and good dipping of the second dipping is determined by confirming a mark displayed at a certain height of the seed.

The mark can be formed by providing barium hydroxide on the surface of the seed.

The mark may be formed as a depression in the seed.

The cross-section of the seed may be square, and the cross-section of the mark may be circular.

Measurement of the brightness of the meniscus can be accomplished by dipping the seed into the silicon melt in an imaging device and photographing the shape of the meniscus at the melted portion.

The method for growing a silicon single crystal may further include a step of determining that the first dipping is good dipping when the brightness of the meniscus shape becomes higher than a preset value and starting necking of the silicon single crystal.

When polycrystallization of a silicon single crystal is detected, a step of secondary dipping of the seed in the direction of the silicon melt can be performed.

A method for growing a silicon single crystal may further include a step of judging the second dipping as good dipping and restarting necking of the silicon single crystal.

According to the method for growing a silicon single crystal according to the present invention described above, when dipping the seed, it is possible to confirm whether the seed has been properly dipped by using an imaging device or by forming a barium hydroxide mark or depression in the seed, so that the silicon single crystal can be properly grown without occurrence of crystal defects through the subsequent necking process.

FIG. 1 is a drawing showing a method for growing a silicon single crystal according to one embodiment of the present invention.
Figure 2 is a drawing showing a silicon single crystal growth device according to the method of Figure 1.
Figure 3 is a drawing showing the shape of the meniscus when the seed is dipped in a silicon melt.
Fig. 4 is a drawing showing one example of the shape of a seed used in the method of Fig. 1.
FIG. 5 is a drawing showing another embodiment of the shape of the seed used in the method of FIG. 1.

Hereinafter, the present invention will be described in detail with reference to examples to specifically explain the invention, and in order to help understanding the invention, the invention will be described in detail with reference to the attached drawings.

However, the embodiments according to the present invention can be modified in various different forms, and the scope of the present invention should not be construed as being limited to the embodiments described below. The embodiments of the present invention are provided to more completely explain the present invention to a person having average knowledge in the art.

Additionally, relational terms such as “first,” “second,” “upper,” and “lower,” as used hereinafter, may be used only to distinguish one entity or element from another, without necessarily requiring or implying any physical or logical relationship or order between such entities or elements.

The method for growing a silicon single crystal according to the present invention measures the brightness of a meniscus shape when dipping a seed to determine whether or not good dipping has occurred, and if it is determined to be good dipping, necking is started to grow a silicon single crystal, and if a problem such as polycrystallization occurs thereafter, the previously grown portion is melted and the seed is dipped again. At this time, the determination of good dipping can be made by checking a mark indicated on the seed.

FIG. 1 is a drawing showing a method for growing a silicon single crystal according to one embodiment of the present invention, and FIG. 2 is a drawing showing a device for growing a silicon single crystal according to the method of FIG. 1. Hereinafter, with reference to FIG. 1 and FIG. 2, one embodiment of a method for growing a silicon single crystal according to the present invention will be described.

The growth device (100) used for growing a silicon single crystal according to the present invention may include a chamber (10) in which a space is formed inside where a silicon single crystal (Ingot) is grown from a silicon melt (Si melt), an internal quartz crucible (20) and an external graphite crucible (25) that accommodate the silicon melt, a heating unit (40) that heats the quartz crucible (20) and the graphite crucible (25), a heat shield (50) that is provided on top of the silicon melt and blocks the heat of the heating unit (40) directed toward the silicon single crystal (Ingot), a support member (30) that is rotated by a driving means to rotate and elevate the graphite crucible (25), a cable (80) that hangs a seed on a seed chuck (85) and lowers it in the direction of the silicon melt, and imaging devices (60) that are provided on the upper part of the chamber (10) and measure the surface temperature of the silicon melt (Si). there is.

The chamber (10) may have a cylindrical shape with a cavity formed inside, and a quartz crucible (20) and a graphite crucible (25) are provided in the central region of the chamber (110). The quartz crucible (20) has an overall concave shape that directly receives a silicon melt, and the graphite crucible (25) surrounds and supports the outer surface of the quartz crucible (20).

In order for the imaging devices (60) to be able to photograph the interior of the chamber (10), the chamber (10) may be provided with a view port in the optical path between the imaging devices (60) and the silicon melt. The imaging devices (60) can photograph the shape of the meniscus and also measure the temperature when the seed is dipped in the silicon melt, as described below, and may include, for example, a CCD camera.

When growing a silicon single crystal using the growth device (100) described above, the cable is first lowered to dip the seed into silicon melt (Si melt) (S110). This dipping may be referred to as the first dipping.

When a relatively low-temperature seed is preheated inside a chamber and rotated at a speed of 1 to 10 millimeters per minute (mm/min) toward a high-temperature silicon melt and lowered, the seed is dipped into the silicon melt, and at this time, a portion of the seed in contact with the silicon melt melts and the brightness increases. The outline of the aforementioned portion can be called a meniscus. In other words, the meniscus is a thin band formed when the silicon melt adheres to the solid seed due to surface tension.

Figure 3 is a drawing showing the shape of the meniscus when the seed is dipped in the silicon melt. The shape of the meniscus is observed by photographing the part where the seed is dipped in the silicon melt (Si melt) with an imaging device.

And, whether the first dipping is performed well, i.e., good dipping is determined (S115), which can be done by measuring the brightness of the meniscus. Specifically, if the brightness of the meniscus is measured by an imaging device and continuously monitored, a section in which the brightness of the meniscus rapidly increases occurs, at which time the seed is determined to have been well dipped, and the descent of the seed is stopped.

That is, if the brightness of the meniscus rises rapidly and is detected to be higher than the preset value, it is judged as good dipping (Yes), otherwise it is judged as not having good dipping (No).

When good dipping is determined from the brightness measurement of the meniscus, growth of a silicon single crystal (Ingot) begins (S130). The growth of a silicon single crystal is accomplished through a necking process in which a neck portion extends with a small diameter from a seed is grown, a shoulder portion in which a diameter rapidly increases from the neck portion, a body portion that is to be used as a silicon wafer through processing is grown, and a tail portion in which a diameter rapidly decreases to complete the growth of the silicon single crystal.

In addition, if it is determined that good dipping has failed because the brightness of the meniscus does not reach a preset value or higher, the seed is further lowered in the direction of the silicon melt to perform a second dipping (S120).

In the second dipping, the seed may be dipped into the silicon melt more deeply than in the first dipping. At this time, a mark is formed at a certain height of the seed. By checking the mark, it is possible to determine whether the second dipping is good (S125). The mark may be barium hydroxide or a relatively small depression as described below. It may be more accurate to observe or measure barium hydroxide or the depression in the second dipping than to determine the increase in brightness of the meniscus in the first dipping.

FIG. 4 is a drawing showing one embodiment of the shape of a seed used in the method of FIG. 1, and FIG. 5 is a drawing showing another embodiment of the shape of a seed used in the method of FIG. 1.

In the embodiment illustrated in FIG. 4, barium hydroxide (Ba(OH) ₂ ) may be provided on the surface of the seed at a certain height. The barium hydroxide layer on the surface of the seed at a certain height can be photographed with the aforementioned imaging device at the moment when the corresponding height of the seed is immersed in the silicon melt, thereby confirming that the seed is dipped to a certain height or part. Even if the barium hydroxide reaches the silicon melt and melts, it may not affect the quality of the grown silicon single crystal.

In the embodiment illustrated in Fig. 5, the seed is provided with a width narrower than that of other parts at a certain height, i.e., a recessed portion is formed. The seed typically has a rectangular cross-section, but through processing such as grinding, the cross-section of the seed in the recessed portion can have a circular shape.

At this time, the length of the diagonal of the cross-section of the seed having a square shape may be about 25 to 30 millimeters, but the diameter of the cross-section of the seed processed into a circle may be about 20 millimeters.

The above-mentioned barium hydroxide layer or depression can form a dipping limit line of the seed, that is, when the barium hydroxide layer or depression dipped in the imaging device, the descent of the cable could be stopped, thereby stopping the descent of the seed.

And, if the second dipping fails to result in good dipping (No), it is judged that it is difficult to grow a silicon single crystal through dipping of the seed, and the seed can be replaced.

Additionally, if the second dipping is judged to be good dipping (Yes), the growth of the silicon single crystal (Ingot) can be restarted (S130).

And, it is possible to determine whether structure loss such as polycrystallization occurs during the growth of a silicon single crystal or whether other crystal quality problems occur (S140). If no crystal quality problems occur (No), the growth of the silicon single crystal continues (S160), and if a crystal quality problem occurs (Yes), the cable is lowered to re-melt the previously grown silicon single crystal by immersing it in a silicon melt (S150).

In addition, the second dipping process (S120) of the seed described above and the good dipping judgment process (S125) of the second dipping can be performed again.

Therefore, if the second dipping fails to result in good dipping (No), it is judged that it is difficult to grow a silicon single crystal through dipping of the seed, and the seed can be replaced.

Additionally, if the second dipping is judged to be good dipping (Yes), necking can be started to resume the growth of the silicon single crystal (ingot) (S130).

And, when the silicon single crystal continues to grow (S160) without causing structural loss such as polycrystallization or other problems in crystal quality, and the growth of the neck portion, shoulder portion, body portion, and tail portion is completed, the growth process of the silicon single crystal is completed.

And, after the growth and impression of the silicon single crystal are completed, a silicon wafer can be manufactured by performing processes such as a cutting process, a grinding process, a polishing process, and a hardening and cleaning process.

The method for growing a silicon single crystal according to the present invention described above can confirm whether the seed has been properly dipped, particularly by using an imaging device when dipping the seed, or by forming a barium hydroxide mark or depression in the seed, so that the silicon single crystal can be properly grown without occurrence of crystal defects through a subsequent necking process.

Although the embodiments of the present invention have been described in more detail with reference to the attached drawings, the present invention is not necessarily limited to these embodiments, and various modifications may be made without departing from the technical idea of the present invention. Accordingly, the embodiments disclosed in the present invention are not intended to limit the technical idea of the present invention, but to explain, and the scope of the technical idea of the present invention is not limited by these embodiments. Therefore, it should be understood that the embodiments described above are exemplary and not restrictive in all aspects. The protection scope of the present invention should be interpreted by the following claims, and all technical ideas within a scope equivalent thereto should be interpreted as being included in the scope of the rights of the present invention.

10: Chamber 20: Quartz crucible
25: Graphite crucible 30: Support member
40: Heating section 50: Heat shield
60: Image capture device 80: Cable
85: Seed chuck 100: Silicon single crystal growth device

Claims (8)

A step of first dipping by lowering the seed from above the silicon melt; and
If the first dipping is determined not to be a good dipping, a step of dipping the seed a second time in the direction of the silicon melt is included;
Good dipping of the above first dipping is judged by measuring the brightness of the meniscus shape, and good dipping of the above second dipping is judged by checking the mark displayed at a certain height of the seed.
The above mark is a method for growing a silicon single crystal in which barium hydroxide is formed on the side of the seed. delete delete delete In the first paragraph,
A method for growing a silicon single crystal, wherein the measurement of the brightness of the above meniscus is performed by dipping the seed into the silicon melt with an imaging device and photographing the shape of the meniscus of the melted portion. In the first paragraph,
A method for growing a silicon single crystal, further comprising the step of determining the first dipping as good dipping and starting necking of the silicon single crystal when the brightness of the above meniscus shape becomes higher than a preset value. In Article 6,
A method for growing a silicon single crystal, comprising: detecting polycrystallization of the silicon single crystal; performing a step of second-dipping the seed in the direction of the silicon melt. In Article 7,
A method for growing a silicon single crystal, further comprising the step of judging the second dipping as good dipping and restarting necking of the silicon single crystal.