JP2783624B2 - Single crystal manufacturing method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for producing a single crystal typified by silicon, germanium, etc., and more particularly to a method for producing a single crystal by a continuous pulling method to which a pulling method (Czochralski method) is applied. The present invention relates to a method for producing a crystal.

(Prior Art) At present, silicon, germanium, and the like are known as semiconductors widely used industrially as devices such as integrated circuits (ICs) and large-scale integrated circuits (LSIs).

Single crystals such as silicon and germanium used in the semiconductor industry use a polycrystal as a raw material, create a molten zone by induction heating on a polycrystal rod, move it from the seed crystal side, and float it to grow a single crystal. Floating Zone
(Hereinafter abbreviated as FZ method) or a pulling method (Czochralski) in which a polycrystal is placed in a crucible and heated and melted, and a seed crystal is immersed in a melt and pulled up to grow a single crystal of a round bar.
Method, hereinafter abbreviated as CZ method).

These production methods are selected according to the use of the single crystal, the single crystal manufactured by the FZ method is used for high resistivity applications, and the single crystal manufactured by the CZ method is used for low to medium resistivity applications.
In recent years, one electronic circuit has become smaller and smaller due to advances in LSI manufacturing technology. On the other hand, the area of a single crystal wafer to be processed has been increased to increase the number of circuits formed in the wafer in one process. By doing so, the cost per circuit is reduced. For this reason, single crystal manufacturing technology is constantly required to have a large diameter, and at the same time,
A method of increasing the length of one single crystal is also being pursued in order to increase the productivity per unit time during the production of a single crystal. The above-mentioned CZ method not only has the advantage that a large-diameter single crystal ingot can be easily obtained, but also advances in technological improvements such as automatic diameter control and semi-continuous operation by recharging the raw material polycrystal, and the FZ method is cost-effective. The fact is that it surpasses the law.

Conventional single-crystal production by the CZ method, in the case of silicon, for example, places polycrystalline silicon as a raw material or polycrystalline silicon and a dopant (additive) in a quartz crucible supported by a support stand in a chamber. After that, under an argon atmosphere, the raw material was melted by a heater arranged around the quartz crucible, and a thin seed crystal made of silicon single crystal was attached to a chuck of a pulling device provided above the crucible, and Is immersed in the raw material melt in the crucible, and then pulled up at a predetermined speed while rotating the pulling shaft relatively to the crucible. Then, a single crystal grows sequentially at the lower end of the seed crystal attached to the pulling shaft. When a dopant is added, a single crystal ingot having a desired resistance value can be obtained depending on the concentration.

A method of continuously pulling a single crystal by such a CZ method is already known. However, according to the continuous pulling method, the dopant concentration in the pulling direction can be made uniform and the surface of the molten liquid can be improved. Can be kept constant, and the yield of the manufactured single crystal can be improved.

JP-B-59-33,551 (JP-A-57-179,096) discloses a method for producing a single crystal by a continuous pulling method. In this manufacturing method, first, as shown in FIG. 8, the tip of a seed crystal 2 attached to a pulling shaft 1 is immersed in a melt 3 to pull up while controlling the temperature and / or pulling speed of the melt 3. Raise axis 1. At this time,
A single crystal C1 is grown continuously at the lower end of the seed crystal 2,
When the pulling of the required length is completed, the temperature of the solution 3 and / or the pulling speed are controlled again to reduce the diameter of the lower end of the single crystal C1 (small diameter portion N1). The seed crystal for the second single crystal C2 is provided (see FIG. 9). By successively repeating this operation, a single crystal having a small diameter portion formed at the lower end is continuously produced.
In the state shown in FIG. 10, the side surface of the single crystal C2 is rotated by the supporting device 4 which is synchronized with the pulling shaft 1 and whose central axis rotates coincident with the pulling shaft 1 and moves at the same speed as the pulling shaft 1. To support. Next, as shown in the figure, the narrow portion N1 between the single crystal C1 and the single crystal C2 is cut by the laser cutting device 6, and the single crystal C1 is collected. In addition, the second and subsequent single crystals
In order to collect C2, C3, C4..., It is configured in the same manner as the support device 4 and rotates in synchronization with the pulling shaft 1 and the center axis coincides with the pulling shaft 1, and moves at the same speed as the pulling shaft 1. Is provided, and the n-th single crystal Cn and the (n + 1) -th single crystal Cn cooperate with the support device 4 described above.
By supporting +1, single crystals can be recovered while performing continuous pulling (see FIGS. 11 and 12).

(Problems to be Solved by the Invention) However, according to such a conventional method for manufacturing a single crystal, as shown in FIG. 10, the (n + 1) th single crystal Cn + 1 is supported by the support device 4. When the small diameter portion Nn of the n-th single crystal Cn is determined by the above, the vibration caused by the cutting propagates to the growth portion of the (n + 2) -th single crystal Cn + 2, and the (n + 2) -th single crystal Cn + 2 is present. The problem of dislocation occurred.

Thus, the present inventors have proposed that dislocations are caused by the size of the temperature gradient and uneven temperature distribution in the growing crystal,
In the small diameter part, the stability of the non-dislocation state is high, and
Based on the finding that if a seed crystal (diameter reduction) operation is performed at the beginning of growth, even a dislocated single crystal has a so-called dash effect, even dislocation-free single crystals, the propagation of vibration due to cutting is approved. After extensive research, the (n +
If a single crystal grown before the n-th is cut at the time of forming a small diameter portion in the 1) -th single crystal, the (n + 2) -th single crystal is present even if the cutting vibration is propagated. It has been found that dislocation is difficult to occur, and even when the small-diameter portion is dislocated, dislocation is easily eliminated, and the present invention has been completed.

The present invention has been made in view of such problems of the related art, and improves the quality and the material yield by continuously pulling a single crystal without causing dislocation, thereby improving productivity. The purpose is to increase.

(Means for Solving the Problems) The present invention for achieving the above object melts raw materials,
There is a single crystal manufacturing method in which a single crystal is grown at the rear end of the seed crystal by pulling up the seed crystal after dipping the seed crystal in the melt, and after growing the n-th single crystal. Forming a small-diameter portion at the rear end of the single crystal without separating the n-th single crystal from the melt,
Further, in the method of continuously producing a (n + 1) th single crystal having the small diameter portion by continuously growing the (n + 1) th single crystal on the small diameter portion and repeating this process, A method for producing a single crystal, characterized in that when forming a small-diameter portion at the rear end of the subsequent single crystal, the single crystal grown before the n-th is cut and collected.

(Operation) In the present invention configured as above, the (n + 1) th
Since the single crystal grown before the n-th is cut when forming the small diameter portion at the rear end of the single crystal after the n-th, the vibration at the time of cutting is caused by the surface of the melt. And propagates to the growing small diameter portion. In such a small diameter portion, there is little difference in temperature gradient and unevenness of temperature distribution in the crystal,
Since the stability of the dislocation-free state of the single crystal is extremely high, dislocations can be prevented. Moreover, in the small diameter part,
Even if dislocation of the single crystal occurs, the single crystal can be continuously pulled up in a dislocation-free state because dislocation is easily caused by the so-called dash effect.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

1 to 5 are sectional views showing a manufacturing method according to an embodiment of the present invention, FIG. 6 is a process diagram of the embodiment, and FIG. 7 is a sectional view showing a pulling device used in the embodiment. is there.

The present invention can be implemented using a conventionally known continuous allocation device. For example, the continuous pulling apparatus in the present embodiment has a chamber 10 including a heating chamber 11 and a pulling chamber 12, as shown in FIG. A graphite crucible 13 and a quartz crucible 14 supported by a graphite pan are provided in the heating chamber 11, and the graphite crucible 13 and the quartz crucible 14 are driven by a driving device via a rotating shaft 15.
16 to rotate. Around a graphite crucible 13 and a quartz crucible 14 formed in a substantially cylindrical shape,
A heater 17 is provided to melt the polycrystalline raw material contained in the quartz crucible 14. Heater 17
Can be used either by a resistance heating method or by an induction heating method, but when applied to a large continuous pulling device, a resistance heating heater is used in consideration of economy. Is preferred.

In the quartz crucible 14, an annularly formed partition wall 18 is provided, whereby the quartz crucible 14 is divided into a melting zone 19 and a suspected zone 20. Both zones 19 and 20 through the communication opening (not shown)
Are communicating. To the melting zone 19, polycrystal or polycrystal as a raw material and a dopant are supplied from a raw material supply device 21 via a nozzle 22. Note that “23” is a heat insulating plate for preventing heat from being radiated from the heater 17.

A pulling device 24 is provided on the upper part of the pulling champ 12 so that the pulling wire 1 serving as a pulling shaft is rotated and moved up and down. A chuck 25 is attached to the tip of the pulling wire 1, and this chuck 25
After the seed crystal 2 is gripped, the pulling device 24 is driven to lower the pulling wire 1 until the tip of the seed crystal 2 is immersed by a predetermined amount in the melt 3 in the crucible 14 made of quartz. If you raise while controlling the pulling speed,
The single crystal C grows at the lower end of the seed crystal 2.

In this embodiment, two supporting devices 4, 5 and a cutting device 6 are provided in the chamber 10 at a position where the grown single crystal C is cooled to a predetermined temperature. The mounting positions of these supporting devices 4, 5 and cutting device 6 are not limited to the positions shown in FIG.
May be set to a position where the single crystal C is in a cooled state so that the single crystal C can be gripped by the support device 4.

Each of the supporting devices 4 and 5 includes a gripper that grips the side surface of the single crystal C, and a driving unit that opens and closes the gripper to operate the position where the single crystal C is gripped and the position where the single crystal C is opened. The lifting device 24 is configured to be able to move up and down in synchronization with the lifting device 24. Further, a cutting device 6 is provided between the two supporting devices 4 and 5 to cut and collect the single crystal. In this embodiment, the support device 4 is provided in the heating chamber 11, and the support device 5 and the cutting device 6 are provided in the pulling chamber 12. Further, although not shown, the single crystal C cut by the cutting device 6 is taken out from a collection door opened in the pulling chamber 12.

Next, a method of manufacturing a single crystal according to the present embodiment using the above-described continuous pulling apparatus will be described. The production method of the present invention
The present invention can be applied to a silicon crystal, a germanium crystal, a gallium-arsenic crystal, a metal crystal, and a metal oxide crystal.

Hereinafter, a production example of a silicon single crystal to which a dopant is added will be described.

First, a predetermined amount of a polycrystalline raw material and a dopant to be added thereto are supplied from a raw material supply device 21 to a melting zone 19 in a quartz crucible 14, and the heater 17 is operated to be melted. The raw material dissolved in the dissolving zone 19 flows to the solidification zone 20 through the communication port of the annular partition wall 18. When the crucible 14 is filled with the melt 3 before starting the pulling, the polycrystal and the dopant can be supplied to both the solidification zone 20 and the melt zone 19. When pulling up, blow argon gas into the heating zone 11,
The heating zone 11 is set to a reduced pressure argon atmosphere.

Next, the seed crystal 2 having a predetermined plane orientation is attached to the chuck 25 of the pulling shaft 1, and the pulling device 24 is operated to lower the pulling shaft until the lower end of the seed crystal 2 is immersed in the melt 3.

At the beginning of the pulling, as shown in FIG. 1, the diameter of the seed crystal 2 is set to 3 to 4 mmφ and the length is set to 50 to 150 mm by setting a high pulling speed and / or increasing the melt temperature.
The diameter is reduced to about mm, and dislocations are driven out to the surface of the seed crystal 2 to eliminate dislocations (high-speed pulling step 30 in FIG. 6). Subsequently, the single crystal C1 having a desired diameter is grown by lowering the pulling rate and / or the temperature of the solution (low-speed pulling step 31 in FIG. 6). In this case, the drive
It is preferable that the quartz crucible 14 is rotated by 16 and the pulling shaft 1 is rotated in a direction opposite to this rotation so as to stir the melt 3 and make the melt temperature uniform.

As shown in FIG. 2, when the first single crystal C1 has grown to a desired length, the pulling speed and / or the melt temperature are increased again to make the rear end of the single crystal C1 thin. Squeeze (high-speed pulling process 32 in FIG. 6). The diameter of the small-diameter portion N1 is preferably formed to be 30 mm or less, particularly, about 4 to 8 mm.

Although not shown in FIGS. 1 to 5, while the pulling operation of the present embodiment is being performed, the melting zone of the quartz crucible 14 from the raw material supply device 21 shown in FIG.
A polycrystal and a dopant are supplied to 19 so that the liquid level of the melt 3 is always kept constant.

Next, as shown in FIG. 3, the pulling rate and / or the temperature of the melt are lowered again to grow the second single crystal C2 (slow pulling step 33 in FIG. 6). At this time, the small-diameter portion N1 formed at the rear end of the first single crystal C1 serves as a seed crystal to grow a second single crystal. Further, as shown in FIG. 4, when the second single crystal C2 has grown to a desired length, the pulling speed and / or the temperature of the melt are increased again to increase the rear end of the single crystal C2. (High-speed pulling step 34 in FIG. 6). The diameter of the small-diameter portion N2 is 30 mm or less similarly to the small-diameter portion N1 described above,
Preferably, it is formed to 8 mm.

Here, while growing the small-diameter portion N2 at the rear end of the second single crystal C2, the second single crystal C2 is supported by the support device 4.
6), the supporting device 4 is raised at a speed equal to the raising speed of the pulling shaft 1, and the small diameter portion formed at the rear end of the first single crystal C1 is supported.
N1 is cut using the cutting device 6 (cutting step 36 in FIG. 6). In this embodiment, a laser cutting device is used as the cutting device 6, but a known device such as a diamond cutter can be used. As described above, the second single crystal C2 cut by the cutting device 6 is supported by the support device 4, and the support device 4 has a variable ascending speed similar to the pulling shaft 1. The single crystal C2, C even after being separated from the pulling shaft 1.
The lifting operation of 3, ... can be continued.

Further, although it can be said that the second single crystal C2 is supported by the support device 4, the vibration at the time of cutting by the cutting device 6 also propagates to the melt surface and causes dislocations. However, in the present embodiment, the small-diameter portion N2 is pulled up from the melt surface when the vibration propagates, and in such a small-diameter portion, the difference in temperature gradient and the temperature distribution in the crystal. And the stability of the single crystal in a dislocation-free state is extremely high, so that dislocations can be prevented. In addition, even if dislocation of the single crystal occurs in the small-diameter portion, the single crystal can be continuously pulled up in a dislocation-free state because dislocation is easily caused by a so-called dash effect.

As described above, in the present embodiment, the cut portion is the small-diameter portion N1, but the cut portion of the present invention is not limited to the small-diameter portion, and may be another portion.

With reference to FIG. 5, the second and subsequent single crystals are generalized and described. Here, the n-th grown single crystal is Cn, and the (n + 1) -th grown single crystal is
.., The small diameter portion formed at the rear end of the n-th single crystal is referred to as Nn, and the small diameter portion formed at the rear end of the (n + 1) -th single crystal is referred to as Nn + 1. .

After recovering the first single crystal C1 from the state shown in FIG. 4, the second single crystal C2 is supported by the support device 4, and the third single crystal C2 While growing the second single crystal C3, the second single crystal C2 also rises, but the ascending limit of the supporting device 4 (the heating chamber 11 shown in FIG. 7).
When the supporting device 4 rises to (upper portion of) the other supporting device 5 descends to support the single crystal C2, the supporting device 4 releases the support of the single crystal C2 and descends to the original position. By supporting the single crystals continuously manufactured in this way by the two support devices 4 and 5 alternately, the support device 5 functions as the pulling shaft 1 when pulling the first single crystal C1. Will fulfill. Therefore, in a state where the n-th single crystal Cn + 1 is supported by the support device 5 while the (n + 1) -th single crystal Cn + 1 is supported by the support device 4, the two support devices 4 and 5 are synchronized. At the rear end of the (n + 1) -th single crystal Cn + 1.
While growing Nn + 1, the cutting device 6 cuts and collects the n-th single crystal Cn. The vibration caused by this cutting is
The light propagates through the (n + 1) -th single crystal Cn + 1 to the melt surface. Since the single crystal growing from this liquid surface has a small diameter, the temperature inside the crystal at the small-diameter portion Nn + 1 is small. Since the difference in gradient and the unevenness of the temperature distribution are small and the stability of a single crystal in a non-dislocation state is extremely high, dislocation can be prevented. In addition, even if dislocation of the single crystal occurs in the small-diameter portion, the single crystal can be continuously pulled up in a dislocation-free state because dislocation is easily caused by a so-called dash effect. Further, the (n + 1) th single crystal Cn + 1 is grown by using the small diameter portion Nn formed at the rear end of the nth single crystal Cn as a seed crystal.

The present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the gist of the present invention.

For example, in the above embodiment, the n-th single crystal is cut while growing a small-diameter portion at the rear end of the (n + 1) -th single crystal while supporting the (n + 1) -th single crystal. However, the present invention is not limited to the above-described embodiment, and when forming a small-diameter portion at the rear end of the (n + 1) -th and subsequent single crystals, it is grown before the n-th. The single crystal may be cut.

(Effects of the Invention) As described above, according to the present invention, it is possible to continuously pull a single crystal without dislocations, thereby improving quality and material yield and increasing productivity. be able to.

[Brief description of the drawings]

1 to 5 are cross-sectional views showing a manufacturing method according to an embodiment of the present invention, FIG. 6 is a process diagram of the embodiment, FIG. 7 is a cross-sectional view showing a pulling device used in the embodiment, 8 to 12 are sectional views showing a conventional manufacturing method. 1 ... pulling shaft, 2 ... seed crystal, 3 ... melt, 4,5 ... support device, 6 ... cutting device, Cn ... nth single crystal, Nn ... nth fine crystal Diameter.

Claims (2)

(57) [Claims] 1. A method for producing a single crystal, comprising melting a raw material, immersing the seed crystal in the melt, and then raising the seed crystal to grow a single crystal at the rear end of the seed crystal. After growing the n-th single crystal, a small-diameter portion is formed at the rear end of the single crystal without separating the n-th single crystal from the melt, and further connected to the small-diameter portion. In this method, the (n + 1) -th single crystal is grown at a rear end of the (n + 1) -th single crystal after the (n + 1) -th single crystal is continuously grown by successively repeating this process. A method for producing a single crystal, comprising cutting and collecting a single crystal grown before the nth one when forming a small diameter portion. 2. The method according to claim 1, wherein the single crystal is silicon.