JPH0421585A - Pulling of single crystal - Google Patents

Abstract

PURPOSE:To pull up plural kinds of single crystals having different resistivity and diameters, by dividing the surface of melt in a crucible into an inside zone and an outside zone with a cylindrical partition wall. CONSTITUTION:Plural supporting pieces 9b uprightly stood in the peripheral direction of a main body part 9a of a cylindrical partition wall 9 are engaged with plural holes 8a bored through a tapered part 8c of a radiant screen 8, fixed with pins ad the partition wall a is pulled up so that the partition wall 9 is not brought into contact with a raw material in a crucible 3. Then the crucible 3 is heated by a heater 4, the raw material containing a dopant is heated and melted, the crucible 3 is raised to a pulling position, the screen 8 and the partition wall 9 are dropped, a supporting part 8b of the screen 8 is contacted with a supporting base 2a of a heat insulating wall 2, the lower end of the main body part 9a is immersed in a proper position in the melt and the melt is divided into an inside zone and an outside zone. Then the crucible 3 is rotated through a shaft 3c in the arrow direction, a pulling shaft 5a is dropped, seed crystal 5c is immersed in the inside zone of the partition wall 9, the seed crystal is pulled up while rotating the shaft 5a to grow single crystal 7 under the seed crystal 5c.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a method for pulling single crystals by the Czochralski method (CZ method), and in particular, the present invention relates to a method for pulling single crystals by the Czochralski method (CZ method), and particularly relates to a method for pulling single crystals using the Czochralski method (CZ method). This invention relates to a single crystal pulling method for obtaining crystals.

[Conventional technology]

Silicon (Si) is used as a substrate for semiconductor devices.
) Single crystals are mainly produced by the CZ method.

In this CZ method, a Si raw material is loaded into a rotatable crucible in a chamber, heated and melted by a heater installed on the outer periphery of the crucible, and a seed crystal is immersed in the Si melt, which is then rotated. This is a method of pulling a Si single crystal by growing the Si single crystal at the lower end of the seed crystal by pulling the Si single crystal upward while causing the seed crystal to grow.

With the diversification of semiconductor devices, the uses of such Si single crystals have become diverse and diverse, and it has become necessary to manufacture single crystals with various diameters or resistivities within the single crystal. .

[Problem to be solved by the invention]

The production of single crystals is basically the production of pulled units, and 1
The diameter of the single crystal produced by multiple pulling is the same.

Therefore, when producing single crystals with different diameters, two pulling devices can be used to pull the single crystals with different diameters individually, or after completing the pulling of the single crystal with the first diameter. After the pulled single crystal was taken out from the pulling device, a new single crystal having a second diameter was pulled. Therefore, it is necessary to perform shoulder building in the early stage of single crystal pulling and tail drawing in the latter half of single crystal pulling, each of which has the disadvantage of low product yield. Additionally, the method described below has the disadvantage that it takes several hours to take out the single crystal and pull it up again.

The resistivity in the single crystal is adjusted by adjusting the dopant concentration in the melt in the crucible.

The segregation coefficient of most dopants used when pulling Si single crystals is less than 1, so as the pulling progresses and the amount of melt in the crucible decreases, the dopant concentration in the melt increases and is pulled. The resistivity in the single crystal decreases. Even if you adjust the bepan H8 degree in the melt and start pulling the single crystal so that the target resistivity is achieved, only a small portion that satisfies the target resistivity is obtained, resulting in a decrease in yield. There is a problem that a decrease occurs.

A lifting method that solves these problems is disclosed in Japanese Patent Application Laid-open No. 1983-
It is disclosed in Japanese Patent No. 132584. This pulling method involves pulling a single crystal from a dopant-added melt in a crucible according to a first resistivity standard, adding the dopant again during the process, and then pulling the single crystal according to a second resistivity standard. This is a way to raise it. With this method, it is possible to obtain a single crystal that satisfies multiple resistivity specifications in one single crystal, but when the dopant is re-added to the melt, the melt surface becomes rippled and the single crystal at the growth interface becomes There is a drawback that crystal growth becomes unstable, resulting in dislocations or polycrystals in the single crystal.

By the way, a device with a double crucible structure is known as a pulling device for continuously producing a large amount of single crystals by additionally supplying raw materials to the melt in the crucible while performing pulling (Japanese Unexamined Patent Application Publication No. 1983-1999). 7
9790, etc.). This involves arranging an outer crucible and an inner crucible concentrically, supplying raw materials to the outer melt between the outer crucible and the inner crucible, melting the raw material, and supplying the raw material to the inner melt through a flow hole.
This is a device that pulls single crystals from the inner melt. In such an apparatus, if a dopant is supplied to the outer melt during the pulling process, instability in the growth of the single crystal can be eliminated. However, since the same amount of melt as the decrease in the inner melt is supplied through the flow holes, even if the dopant is supplied to the outer melt, the dopant concentration in the inner melt does not increase much, and the desired concentration is not increased. There is a problem in that it takes time to reach the concentration, and during this time many single crystals that are outside the standard range are pulled. Furthermore, the inner crucible may undergo buckling deformation during melting of the raw materials, making it impossible to pull a single crystal. Furthermore, this double crucible structure has the problem of high manufacturing cost.

The present invention has been made in view of the above circumstances, and it is possible to improve the yield of single crystals without using a double crucible, and to combine multiple types of single crystals with different resistivities and/or diameters into the same single crystal. An object of the present invention is to provide a method for pulling a single crystal that can be pulled continuously into a crystal.

[Means to solve the problem]

The single crystal pulling method according to the first invention of the present application is a method of heating and melting a raw material contained in a crucible and pulling a single crystal from the melt in the crucible, in which the melt is not melted below the surface of the melt in the crucible. A cylindrical partition wall is provided that separates an inner area for pulling the single crystal from an outer area thereof, which extends above and below the melt surface, in a state where the liquids are in communication with each other, and pulls the single crystal from the inner area. The method is characterized in that a dopant is supplied to the outer region at a time of .

A single crystal pulling method according to a second invention of the present application is a method of heating and melting a raw material contained in a crucible and pulling a single crystal from a melt in the crucible, in which the melt is not melted below the surface of the melt in the crucible. A cylindrical partition wall is provided that separates an inner area for pulling the single crystal from an outer area thereof, which extends above and below the melt surface, in a state where the liquids are in communication with each other, and pulls the single crystal from the inner area. At the time of , a dopant is supplied to the outer region, and the diameter of the single crystal being pulled is gradually increased or decreased to a predetermined diameter, so that single crystals with a diameter different from the diameter at the time of the previous pulling are continuously produced. It is characterized by raising the temperature.

A method for pulling a single crystal according to a third aspect of the present application is a method for heating and melting a raw material contained in a crucible and pulling a single crystal from the melt in the crucible. The method is characterized in that the diameter of the single crystal inside is gradually increased or decreased to a predetermined diameter, and single crystals having a diameter different from the diameter at the time of previous pulling are continuously pulled.

[Effect]

In the first invention and the second invention, since the melt surface is divided into the inner region and the outer region by the cylindrical partition wall, even if the dopant is supplied to the melt in the outer region, the melt surface in the inner region There is no ripple, and there is no problem with single crystal growth. Further, since the dopant supplied to the melt in the outer region is dissolved by the entire melt, the dopant concentration in the melt in the inner region quickly changes to a desired concentration, and there is almost no part outside the standard.

Furthermore, in the second and third inventions, since a plurality of single crystals having different diameters are pulled successively, there is little reduction in yield due to the top and tail.

〔Example〕

Examples of the present invention will be specifically described below.

FIG. 1 is a schematic cross-sectional view showing the configuration of an apparatus for carrying out the single crystal pulling method according to the present invention, in which 1 is a chamber, 2 is a heat retaining wall, 3 is a crucible, and 4 is a heater. ing.

A heat insulating wall 2 is lined around the side of the chamber 1, a crucible 3 is disposed in the center surrounded by the heat insulating wall 2, and a heater 4 is placed between the crucible 3 and the heat insulating wall 2. A gap forming an exhaust air passage is provided between them.

The crucible 3 has a quartz container 3 inside a carbon container 3a.
The upper end of the shaft 3c that penetrates the bottom wall of the chamber 1 is connected to the center of the bottom part, and the chamber 1 can be raised and lowered while being rotated by the shaft 3c. .

A single crystal pulling port 1a, which also serves as a supply port for atmospheric gas (Ar gas) in the chamber 1, is opened in the center of the upper wall of the chamber 1, and a dopant supply port 1b is opened at one location around the single crystal pulling port 1a. It is being A pull chamber 5 is provided upright in the pull-up port 1a, and a dopant supply pipe 6 is inserted into the chamber 1 through the dopant supply port 1b. A chuck 5b is suspended from the upper end of the pull chamber 5 using a pulling shaft 5a to grip the seed crystal 5c, and the upper end of the pulling shaft 5a is connected to a rotating and lifting mechanism (not shown) to hold the seed crystal 5c. After blending with the melt, the single crystal 7 is placed at the lower end of the seed crystal 5c by rotating and raising it.
It is designed to encourage growth.

A radiant screen 8, which is a radiant heat shield, is disposed above the chamber 1 around the pulling area of the single crystal 7, and is movable up and down by a lifting means arranged at the upper part of the inside of the pull chamber protection cylinder 5. This radiation screen 8 has a cylindrical partition wall 9
is installed. The dopant supply tube 6 passes through the radiation screen 8 and its tube end is located above the edge of the crucible 3. The radiation screen 8 has a cylindrical support part 8b on the outer peripheral edge of an annular rim 8a made of carbon, and the inner peripheral edge of the annular rim 8a has a diameter that decreases downward from there to form a hollow inverted truncated cone shape. The tapered portions 8c are each provided with a tapered portion 8c, and are supported on the upper surface of the heat retaining wall 2 by a support portion 8b.

FIG. 2 is a perspective view of the cylindrical partition wall 9. The cylindrical partition wall 9 is made of quartz and has supporting pieces 9b erected from a plurality of circumferential locations at the upper end of the cylindrical partition main body 9a. It is. Each support piece 9b is inserted into a plurality of holes 8d drilled in the tapered part 8c of the radiation screen 8 and fixed with pins, and the cylindrical partition wall 9
is movable in the vertical direction as the radiation screen 8 moves up and down. The position of the cylindrical partition wall 9 can be raised to a position where the lower end of the cylindrical partition wall 9 is not submerged in the melt in the crucible 3 when the radiation screen 8 is raised, and when the radiation screen 8 is lowered. At the same time when the support part 8b of 8 comes into contact with the support base 2a on the upper part of the heat insulation wall 2, the lower end of the cylindrical partition wall 9 is located at a required height from the inner bottom of the crucible 3 and at an appropriate depth in the melt. It is set so that it is immersed up to that point.

Next, the procedure for pulling a single crystal will be explained.

First, the cylindrical partition wall 9 is pulled upward, and the cylindrical partition wall 9 is placed in the crucible 3.
Set it so that it does not come into contact with the raw materials inside.

In this state, the crucible 3 is heated by the heater 4, and the raw material to which the dopant has been added is heated and melted. When the raw materials are melted, the crucible 3 is raised to the pulling position, and the elevating means is activated to lower the radiant screen 8 and the cylindrical partition wall 9, so that the support part 8b of the radiant screen 8 moves up to the support base 2a of the heat retaining wall 2. The two are positioned so that they are in contact with each other and the lower end of the partition main body 9a of the cylindrical partition 9 is immersed at an appropriate position under the melt. By doing this, the melt is in communication with each other below the melt surface in the crucible 3, and the inner region where the single crystal 7 is pulled up and the outer region thereof can be separated from the upper and lower regions including the melt surface. I can do it.

The crucible 3 is rotated in the direction of the arrow by the shaft 3c that supports it, and the pulling shaft 5a is lowered to immerse the seed crystal 5c in the melt in the inner region surrounded by the cylindrical partition wall 9. , pulling shaft 5a
is rotated and pulled up at a predetermined speed to grow a single crystal 7 under the seed crystal 5c. Then, at any time during this pulling, a dopant is supplied into the melt in the outer region through the dopant supply pipe 6 to change the resistivity of the single crystal 7 or change the diameter of the single crystal 7. .

In addition, if the crucible 3 has a sufficient vertical stroke,
It is not necessary to pull up the cylindrical partition wall 9 in advance (it is not necessary to do so. Ar gas is supplied from the supply pipe connected to the upper end of the pull chamber 5 from the start of melting of the raw material contained in the crucible 3 to the end of pulling the single crystal). is introduced from above onto the crucible 3 through the pull chamber 5.The crucible 3 is introduced from above the pull chamber 5.
The Ar gas that has descended is passed through the radiation screen 80 and the tapered part 8.
c, the melt surface in the crucible 3 is reached, and from there it passes through the lower surface side of the radiation screen 8 to the partition main body 9a of the cylindrical partition 9.
and the support piece 9b, then through the outer area surrounded by the cylindrical partition wall 9, through the ventilation path formed between the crucible 3, the heater 4, and the heat retaining wall 2, and then to the lower side wall of the chamber 1. The gas is sucked and discharged from the open exhaust port 1c by an exhaust pump (not shown).

The radiant screen 8, which is a radiant heat shield, has a function of preventing SiO evaporated from the melt surface from solidifying (Sin(gas)-"5in(solid)) by its heat retention effect on the melt surface side. This prevents the evaporated SiO from adhering to the cylindrical partition wall 9 and becoming foreign matter and falling onto the melt surface.

Crucible used in this example 3. The cylindrical partition walls 9 had diameters of 16" and 10", respectively, and the amount of melt before the start of pulling was 45 kg. The single crystal 7 at the start of pulling is a 6"φ P-tope N type <100>, and the single crystal 7 during pulling is 15 rpm and 5 rpm, respectively, and the pulling speed is 1.3 to 1. .5m+=/min.

Further, in order to prevent the dopant supplied from the dopant supply pipe 6 into the melt in the outer region from adhering to the single crystal side during pulling, the cylindrical partition wall 9 was immersed in the melt by about 10 m.

Next, a specific example in which an S1 single crystal was pulled by the method of the present invention using an apparatus as shown in FIG. 1 will be described.

(Example of the first invention) Resistivity range is 8Ω(2) to 12Ωcm and 1.5Ωcm to
3Ω. A P-doped N-type 6"φ Si single crystal with □ was continuously pulled. FIG. 3 is a graph showing the results of such a pulling example and a schematic diagram of the pulled single crystal. In the graph, The solid line (a) shows the results of this example, A shows the time point when the dopant is supplied into the melt via the dopant supply pipe 6, and the broken line (bl shows the result when no dopant is supplied). If dopant is not supplied during pulling, 1.5Ω is continuously applied.
It is not possible to pull a single crystal of Cm~3Ω(2).

However, in this embodiment, since the dopant is supplied at a desired time, it is possible to pull a single crystal of 1.5 ΩC111 to 3 Ω■ following the pulling of a single crystal of 8 ΩC111 to 12 Ω■.

As a result, in this example, almost the entire area of the pulled single crystal can be provided as a product.

(Example of the second invention) 8Ωc11-12Ω country, 6”φ P-doped N type Si single crystal and 1.5ΩCff1-3Ω country, 4”φ P-doped N
type Si single crystal was pulled within the same single crystal. FIG. 4 is a graph showing the results of such a pulling example and a schematic diagram of the pulled single crystal. In the graph, A indicates the point at which the dopant is supplied into the melt via the dopant supply pipe 6 and the diameter starts to gradually decrease. When the calculated resistivity reached 8 Ωcm (Fig. 4A), the dopant was supplied and the diameter started to be gradually reduced to 6"φ - 4"φ, and after reaching 4"φ, the diameter was reduced to 4" Continue lifting at φ.

As can be seen from Figure 4, two types of single crystals with different resistivities and diameters can be continuously pulled within the same single crystal without any time loss and without any loss at the top or tail. As a result, almost the entire area of the pulled single crystal can be used as a product.

(Example of third invention) P-doped N-type Si of 8ΩcIII to 12Ω country, 6″φ
A single crystal and a P-doped N-type Si single crystal of 4ΩCff1 to 8Ω and 4”φ were pulled in the same single crystal. Figure 5 shows a graph showing the results of such a pulling example and a graph of the pulled single crystal. This is a schematic diagram of a crystal. In the graph, A indicates the point at which the diameter of the single crystal starts to gradually decrease. At the point when the calculated resistivity reaches a value of 8Ω (Fig. 5A), the diameter is reduced to 6". φ−
Start the gradual decrease to 4”φ, and after reaching 4”φ
Continue lifting. In addition, in the example of this third invention,
Since no dopant is supplied during pulling, a cylindrical partition wall may not be used. In this example as well, as can be seen from Figure 5, two types of single crystals with different diameters can be continuously pulled within the same single crystal without any time loss and without any loss at the top or tail. As a result, almost the entire area of the pulled single crystal can be used as a product.

In addition, although the above-mentioned example explained the case where two types of single crystals were continuously pulled, the present invention enables continuous pulling of three or more types of single crystals having different resistivities and/or diameters. It goes without saying that there is.

Further, in the above embodiment, the raw material is not supplied during the pulling, but the present invention can also be applied to the case where the raw material is supplied to the melt in the outer region.

Furthermore, although the above-mentioned embodiments have been described with reference to the case where a silicon single crystal is grown, the present invention is not limited to this in any way, and it goes without saying that the present invention can be applied to various types of single crystal growth.

〔Effect of the invention〕

As detailed above, in the single crystal pulling method of the present invention, multiple types of single crystals with different resistivities and/or diameters can be pulled continuously in one pulling process, and the It is possible to improve the ratio. As a result, the present invention makes it possible to produce a wide variety of single crystals at high yields.

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view of a single crystal pulling apparatus used for carrying out the method of the present invention, FIG. 2 is a perspective view of a cylindrical partition wall, FIGS.
5 are diagrams showing the results of a pulling example using the method of the present invention. 3... Crucible 4... Heater 6... Dopant supply pipe 7... Single crystal 9... Cylindrical partition wall 9a... Partition main body portion 9b... Supporting piece patent applicant Osaka Titanium Manufacturing Co., Ltd. Company (1 other person) Agent Patent attorney Noboru Kono] Figure Top Tail Figure Top Figure Le

Claims (1)

[Claims] 1. In a method of heating and melting a raw material contained in a crucible and pulling a single crystal from the melt in the crucible, the melts are in a state of mutual communication below the surface of the melt in the crucible. , a cylindrical partition wall is provided that separates an inner region from which the single crystal is pulled from the inner region and an outer region therefrom above and below the melt surface, the single crystal is pulled from the inner region, and at any time during this pulling, the outer region A single crystal pulling method characterized by supplying a dopant. 2. In a method of heating and melting raw materials contained in a crucible and pulling a single crystal from the melt in the crucible, the melts are in contact with each other below the melt surface in the crucible, including the melt surface. A cylindrical partition is provided above and below the inner region for pulling the single crystal and an outer region thereof, the single crystal is pulled from the inner region, and a dopant is supplied to the outer region at any time during this pulling. In addition, single crystal pulling is characterized in that the diameter of the single crystal being pulled is gradually increased or decreased to a predetermined diameter, and single crystals having a diameter different from the diameter at the time of previous pulling are continuously pulled. Upper method. 3. In a method of heating and melting a raw material contained in a crucible and pulling a single crystal from the melt in the crucible, gradually increasing or decreasing the diameter of the single crystal being pulled at any time during pulling. to change it to the specified diameter,
A method for pulling a single crystal, which is characterized by continuously pulling a single crystal having a diameter different from the diameter at the time of previous pulling.