JPH02116696A - Shell for strengthening quarts crucible - Google Patents

Abstract

PURPOSE: To obtain a shell that does not generate asymmetricalness in a hot field and lowers the impurity level in a working body, by forming the shell of a carbonaceous material having through-holes of a specified area and forming at least one point thereof of pyrolyzable carbon-impregnated carbon fibers.

CONSTITUTION: The shell 2 for reinforcing a quarts crucible 1 used for growing a crystal from a melt is produced by consisting this crucible of a bottom 13 and a side part 12 made of a carbonaceous material, forming this crucible in such a manner that the crucible has the through-holes 14 and the ratio of the total area of the through-holes and the outside area of the crucible 1 is 0.15 to 0.98 and forming the carbonaceous material of at least one point 12 or 14 of the carbon fibers impregnated with 10 to 150% pyrolyzable carbon. The crucible has a high mechanical strength according to the above constitution. Asymmetry in a heat field formed by a heater is not generated. In addition, the chemical effect between the shell and the crucible is lessened and the contact area between both is decreased to decrease the mass of the shell, by which the level of the impurities of the working body is lowered and the reliability of the quartz crucible is enhanced.

COPYRIGHT: (C)1990,JPO

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention This invention relates to techniques for growing crystals from melts, and more particularly to shells for strengthening quartz crucibles used to grow semiconductor crystals.

The present invention is advantageously used to grow septate crystals from molten silicon, gallium arsenide, and other semiconductor It materials. This is because it is applicable in a thermal field that meets the demands of the process conditions with regard to temperature gradients within the melt and crystalline body. In this case, no asymmetry occurs in the thermal field created by the heater. Well, the level of impurities in the working body will decrease and the reliability of the quartz crucible in operation will increase.

The invention also applies to crystal growth processes carried out in the temperature range of 1000 to 2000 °C.

BACKGROUND OF THE INVENTION Graphite shells (as supports, molds, etc.) are widely used to strengthen quartz crucibles. However, as a result of testing various shell structures, there is no shell that can handle a wide range of temperature gradients from melt to crystal. According to such a shell, the thermal field formed by the heater can be regenerated without distortion, the proportion of impurities in the working body will be reduced, and the chemical interaction between the shell and the crucible will lead to the formation of olfactory crystals. When producing quartz crucible (DE, C, 3005492), a quartz crucible (DE, C, 3005492) is used.

According to this shell, the thermal field created by the heater becomes asymmetrical, increasing the temperature gradient in the melt,
The longitudinal temperature gradient during the process is substantially reduced.

Thus, there is a limit to the efficiency of the process. Since the contact area between the shell and the crucible is large, the chemical interaction between them increases the proportion of impurities in the working volume and increases the chance of damage to the crucible during the process. In order to reduce the impurities t'+ in the working volume (furnace chamber), the shell hx is cleaned in Freon. Ikekata: To keep it clean during operation, it is impregnated with graphite pores, pyrolytic carbon, silicon carbide, etc., which increases the manufacturing cost of the shell.

Known shells for strengthening quartz crucibles limit the yield in the manufacturing process and make it impossible to obtain high-quality crystals. Shells according to the prior art also have high manufacturing costs and are difficult to obtain during operation. This results in a decrease in the reliability of the system.

The shell used to strengthen the quartz crucible used to grow crystals from the melt has sides and a bottom made of carbon-based material and has through-holes. (JP, B, 58-140392) is known.

When graphite is used as the shell material, the efficiency of the process is reduced and the quality of the grown crystals is reduced. As is known, during the process the temperature gradient in the region of the melt below the crystal tends to increase, while the temperature gradient along the axis of the crystal tends to decrease, so that the temperature gradient of the crystal by the end of the process tends to increase. Growth rate will be much slower. Due to non-uniform heating around the quartz crucible due to irregular contact with the graphite shell (asymmetry of the heat field in the melt), the melt must be overheated and prevented from being cooled by the crucible wall. It won't happen.

As a result, the crystal growth rate decreases.As is well known, the asymmetry of the thermal field in the melt
is transmitted to the lower zone of the crystal, thereby causing microdefects and imperfections other than f'1 in the structure of the growing crystal. The contact area between the graphite shell and the quartz crucible causes a chemical reaction, so that the products of the chemical reaction enter the melt through the gas phase and then into the crystal, thus allowing the crystal to grow without segregation. Vi is inhibited.

In addition, during storage, transportation and operation, the graphite shell with sufficient porosity reacts with the quartz, thus causing losses to the crucible during the crystal growth course, as is known.
Adsorbs external impurities (alkali, etc.).

One of the reasons why crucibles are damaged during the metal melting stage is the difference in water content between the upper part of the crucible and its bottom. ! Ta. It is also related to the properties of the graphite shell.

By forming a through hole in the shell, the temperature gradient in the lower zone of the crystal is reduced to a certain extent, the longitudinal temperature gradient in the crystal is increased, and the asymmetry of the thermal field in the melt and the region below the crystal is reduced. can reduce gender. This in turn speeds up the crystallization rate (ie, the efficiency of the process) and improves the quality of the grown crystals. However, the disadvantage is that the mechanical strength of the shell is reduced, the corrosion resistance is reduced, and at the same time the cost of manufacturing the shell is increased.

Graphite'tz as the shell material limits the efficiency of the process and limits the quality of the phosphorus crystal.

Even when a strong bluff eye is used, the expulsion of the shell as a ratio between the total area of the through holes and the external surface area of the crucible will not exceed 15.

PROBLEM TO BE SOLVED This invention aims to provide a shell for strengthening a quartz crucible used for growing crystals from a melt, the shell having axial symmetry. 0 materials and structures that allow the thermal field to be transferred to the melt without distortion! This symmetrical heat field is further transmitted to the lower zone of the growing crystal,
A thermal field is formed with a current temperature gradient in the melt and crystal. At the same time, the percentage of impurities in the working content of the crucible and therefore in the crystals is reduced, the corrosion resistance of the quartz crucible is improved11, and the reliability during operation of the crucible is improved. The objective is achieved by a shell used to heat a quartz crucible used to grow crystals from a bath melt. According to the invention, the shell is made of a carbonaceous material and has sides and a bottom with through holes, the carbonaceous material M in at least one part of the shell;
The ratio to the outer surface area of the hot pot is 0.15 to 0.98.

The entire shell or a portion thereof contains 10 pyrolytic carbons.
Since it is made from carbon fiber impregnated to ~150%, a through-hole with a wide diameter is obtained. This is because the mechanical strength and corrosion resistance of this material are higher than those of graphite shells. The range of impregnation is determined experimentally. For example, if the degree of impregnation of the carbon fibers with pyrolytic carbon is less than 10%, the life of the shell will decrease sharply, thus affecting the reliability of the crucible during operation. Even if the degree of impregnation exceeds 150%, the life of the shell will not be particularly extended, and only the manufacturing cost will increase.

The ratio of the total surface area of the through hole to the outer surface area of the crucible is 0.
．． For shells between 15 and 0.98, the thermal fields in the melt and in the crystal have a wide range. This shell does not disrupt the symmetry of the thermal field formed by the heater. The proportion of impurities in the working volume of the growing crystal reduces the contact area between them and the mass of the shell ( (depending on the factor). The relationship between the total surface area of the through holes and the outer surface area of the crucible is preferably determined experimentally from 015 to 098. If this ratio is below % 0.15, the symmetry of the thermal field formed by the heater in the shell, in the lower zone of the crystal and in the melt is distorted;
If this ratio exceeds 0.98, the shell will be compromised during the crystal growth process.

In order to contain crystals with a low carbon content, it is desirable to place the shell within the body of the quartz crucible.

The arrangement prevents carbon from transferring from the shell through the cass phase into the melt and into the growing crystal.

In a shell for reinforcing a quartz crucible, it is desirable that the area of one hole is equal to the area of the stumbling hole on one side with a width of 1@ to 20@ of the thickness of the crucible wall.

As a result, the "transparency" of the shell is maintained over a wide range;
Hole 1 in the 0 shell increases the reliability of the quartz crucible in operation
When the area of the zero hole obtained by experiment is smaller than the thickness of the crucible wall, the symmetry of the thermal field formed by the heater will be lost, but in the melt,
The temperature gradient in the lower zone of the crystal is maintained well. If the surface area of the hole is a square area that is 20 times or more the thickness of the crucible wall, the viscosity of quartz decreases when the temperature exceeds 1700K, and the quartz crucible will be damaged by passing through the hole in the shell. may leak).

Preferably, the thickness Fi of the side part of the shell is 01 to 2.5 fl of the thickness of the cap of the crucible.

Such an arrangement increases the mechanical strength of the shell,
Corrosion resistance of the shell is maintained within a preselected range of "permeability". The thickness of the wall on the side of the shell is determined experimentally, taking into consideration the M-axis property in terms of operational efficiency and manufacturing cost.

If the thickness of the shell wall is 01 of the thickness of the crucible wall,
If it is thinner than twice, the mechanical strength and corrosion resistance of the shell will be insufficient, but on the other hand, if the thickness of the shell is more than 2.5 times the thickness of the crucible wall, the manufacturing cost of the shell will increase;
"Transparency" decreases.

Preferably, the thickness of the bottom of the shell is 1 to 5 times the thickness of the crucible wall.

As a result, the operational reliability of a crucible depends on the temperature difference between its sides and bottom? fnmaru.

The wall thickness range at the bottom of the shell is determined experimentally.

When the wall thickness of the shell is larger than the wall thickness of the crucible, the operational reliability of the shell decreases. On the other hand, when the wall thickness of the shell is more than 5 times the wall thickness of the crucible, the reliability during the operation run of the crucible decreases and the manufacturing cost of the shell increases.

EXAMPLE Strengthening a quartz crucible for growing crystals of molten metal by the Chi-Z key method based on an example of the present invention with reference to the attached drawings below. The shell of the tanu is clearly seen in the diagram ψ1'O ηλ1, which shows that it is not housed in a shell 2 to strengthen the crucible, but is attached to a shaft 3. A thermal unit containing a quartz crucible is shown. The three shafts are connected to a drive arrangement (not shown) for rotation and vertical movement. The crucible ltj, surrounded from the outside by a coaxially arranged resistive heater 4h, forms a thermal field in the melt 5 with a preset temperature gradient. Furthermore, this crucible is surrounded by a heat shield 6. The crystals 7 growing from the melt 5 onto the seeds 8 are located on the upper side @
9, thus performing rotation around the axis and movement in the vertical direction.

The thermal unit is arranged in a chamber 10 and defines a working volume @ 11 for growing crystals 7. The shell 2 for strengthening the quartz crucible includes a side part 12 and a bottom part 13, respectively; Made from carbon-based materials. This shell has a 1L through-hole 14 (see FIG. 2). According to one feature of the invention, at least one part, namely the side part 12 or the bottom part]
Since the shell is made from carbon fiber impregnated with 10 to 50 layers of pyrolytic carbon, the shell 2Fi has increased mechanical strength and improved corrosion resistance.

Figures 1 and 2 show that 10 to 150 pieces of pyrolytic carbon are impregnated. Also shown is a shell 2 with side parts 12 made of carbon fiber collar. The bottom part 13 is made of graphite.

Since the entire shell 2 or a part of the shell is made of carbon fiber impregnated with 10 to 150% pyrolytic carbon'a, the "permeability" of the shell 2 can be varied over a wide range. reliability during operation is maintained. This reliability is due to high mechanical strength and excellent corrosion resistance. This mechanical strength is due to the toughness of the carbon fibers, while the corrosion resistance is achieved by removing dipores by treatment with pyrolytic carbon.

The shell 2 of the invention is also characterized in that the ratio between the total area of the through holes 14 and the external surface area of the crucible 1 is in the range of 0.15 to 0.98.

The permeability of the shell from 015 to 098 provides a wide range of thermal fields within the melt 5 and crystal 7. These advantages are due to the fact that the shell 2 does not function as a heat shield between the melt 5 and the heater 4;
This is different from prior art structures.

Due to the high "transparency" of the shell 2, the heat generated by the heater 4 is transferred to the crystal zone of the growing crystal 7, maintaining the symmetry of the heat field with respect to the trunk of the crystal 7. By uniformly heating the crucible 1, the growth rate of the crystals 7 is increased and the process is terminated due to the low heat conductivity of the shell 2 due to the material used and the ratio between the area of the through holes 140 and the external surface area of the crucible 1. The growth rate remains high until As a result, heat transfer from the shell 2 to the crystal 7 is blocked,
The contact area between the shell 2 and the crucible 1 is reduced, thus reducing the chemical interaction t'i between the two, so that the chamber 1
The proportion of impurities in the working volume 11 defined between 0 and each element of the thermal unit is reduced.

FIG. 3 shows another embodiment of the shell
Since the through hole 17 (shell) 5 is thus arranged, , the proportion of impurities in the working chamber of the growing crystal decreases, which can prevent carbon from transferring from the shell to the bath melt and further into the crystal during pressure growth. The pond embodiment of 18 strengthens the quartz crucible 19 and includes sides 20 and bottom 21.
contains. The sides 20 of the shell 18 are coated with 1 pyrolyzable carbon.
Made of 0-150% impregnated carbon fiber,
On the other hand, the bottom part 21 is made of graphite, and the hole 22 of the shell 18 has one surface, and preferably has a side of the wall thickness (L) of the crucible 19 from 1 to 20@. The surface area of This desired range is necessary to preserve the reliability of the crucible 19 during operation while ensuring maximum "transparency" of the shell 18.

FIG. 5 shows a shell 23 for strengthening the quartz crucible 24.
An example of a pond will be shown, but this specific example has a side part 25 and a part 2.
It has 6. The two parts 25, 26 of the shell 23, the two parts of the whole shell 230, contain 1 pyrolytic carbon.
The wall thickness of the side 25 of Rochelle 23 made from carbon fiber impregnated with 0-150% "KJke, Crucible 2"
The wall thickness t of 4 is within the range of 01 to 2.5@.

The wall thickness (m) of the bottom part 26 of the shell 23 is within the range of 1 to 5 @ of the wall thickness t of the crucible 24.
rnJ, in order to minimize the manufacturing cost of the shell 23,
The selection is made to preserve operational reliability of the shell 23 of the crucible 24.

The side 25 and bottom 26 of the shell 23 have through holes 27 and 28, respectively. The shape of these holes 27 and 28 may be changed; for example, the side 25 of the shell 23 may have a mesh with holes 27 in the shape of a rhombus (see FIG. 5). On the other hand, @ section 26V of shell 23! , triangular hole 28
(See FIG. 6) It may also be in the form of a mesh.

2.15.18 The shape of the shell as shown in Figures 1-6.
．． 23, holes 14.17.22.
27%28 total area, fY 1.16.19.2
4 to the outer surface area is reliably between 0.15 and 0.98
falls within the range of

In addition to the advantages of forming a thermal field, reducing the proportion of impurities in the chamber, and increasing reliability during operation of the quartz crucible, the present invention provides advantages for the process by forming a shell. Power can be saved, the consumption of high-purity graphite can be reduced, and the size of the crucible can be increased.

The shell of Tanu reinforcing a quartz crucible operates as follows.

Crystalline silicon is charged into a quartz crucible, and the crucible 1
is placed in shell 2. Next, crucible 1tI′i
, a heater 4 and a heat shield 6. chamber 10
It is attached to the inner shaft 3. The chamber is then pressure-sealed and the interior is evacuated. Argon is injected. Heater 4 is switched on and 1
brought to a temperature of 900°C. Heater 4 also radiates heat to the crystalline silicon, causing it to melt in the crucible (melting point is 1690°C) "Transparent"
A shell 2 is interposed between the heater 4 and the silicon melt 5. After the silicon has melted, the seed 8 attached to the shaft 9 sinks into the melt 5. By rotating and moving the shaft 9, the crystal 7 is pulled up to the seed 8.

The shell 2 containing the crucible 11 reduces the temperature gradient in the uncrystallized region and increases the axial temperature gradient in the crystal. Because of this, the asymmetry of the thermal field within the melt is reduced, resulting in an increased crystal growth rate and increased crystal quality.

In addition, the contact area between the shell and the crucible is also substantially KM little, which reduces the quality of the products of the chemical reactions in the working volume and reduces their crystalline state, as a result of which the quality of the crystals improves. .

Although specific examples of the present invention have been described above, the present invention is not limited to these. Pond embodiments are possible without departing from the scope and spirit of the invention as claimed.

Effects of the Invention The carbon fiber shell impregnated with 10-150% pyrolytic carbon is characterized by high mechanical strength and excellent thermal and chemical stability.

Ratio between the total area of the through-hole and the outer area of the crucible, 015
Configuring the shell to have ~0.98'e ensures the formation of a thermal field within the melt and crystals over a wide area.

The shell does not create an asymmetrical thermal field. The proportion of impurities in the working volume of the growing crystal reduces the chemistry between the shell and the crucible,
This can be achieved by reducing the contact area between the two and reducing the mass of the shell.

Placing the shell within the crucible prevents carbon migration into the melt and through the gas phase to the growing crystal.

The shell of the present invention has one hole with an area equal to the area of a square with one side having a width of 1 to 20 times the thickness of the crucible wall.The shell of the present invention has a high degree of "transparency". Maintains reliability during operation of quartz crucibles.

By providing the shell with side walls of a thickness equal to 01 to 2.5 times the wall thickness of the crucible, a high mechanical strength is achieved within a preselected "permeability" range.

In addition, the bottom of the shell has a thickness equal to 1 to 5 times the crucible wall thickness, increasing the reliability of the crucible during operation.

[Brief explanation of the drawing]

FIG. 1 is a vertical cross-sectional view of a thermal unit with a shell for strengthening a quartz crucible used for growing crystals of silicon by the Chickralski method. FIG. 2 is a cross-sectional view of a shell used to strengthen a quartz crucible according to the present invention. FIG. 3 is a vertical sectional view showing a reinforcing shell within a quartz crucible. FIG. 4 is a vertical cross-sectional view showing a companion shell reinforcing a quartz crucible with sides made of carbon fiber and a bottom made of graphite. FIG. 5 shows a vertical cross-section of a quartz crucible with a reinforcing shell with a bottom 8'Is made of carbon fiber. FIG. 6 is a vertical sectional view showing the bottom of a shell for reinforcing a quartz crucible made of carbon fiber. 1: Melt #Y2 Nigel 3: Shaft 4: Resistance heater 5: Melt 6: Heat shield 7: Growing crystal
8: Seed 9: Shaft 10: Chamber 11:
Working volume of growing crystal i1 12 Side part of Nigel 13 Bottom of Nigel 14: Through hole 15 Nigel 1
6: Crucible 17: Through hole 18 Ni 19: Crucible 20: Side 21: Bottom 22: Through hole L: Crucible wall thickness 23 Ni 24: Crucible 25: Side 26: l1i
EII K side wall thickness t: crucible wall thickness m bottom wall r! ! -27: Through hole 2
8: Penetrating A hole patent applicant agent Patent attorney Fumi Sato (1 person) F/, 2 f'/G, 7 0 shots 0 shots 0 shots 0 shots Eduard Vladimirovich Mikhail Grankovsky Gennadayevitsch Bushev Vladaymir Vladimirovitch Kostein Aleksandr Ivanovitch Ogurtosov Soviet Union Moskovskaya Oblast Bodolsk Okteabrskie Brospekt 5 Kwarchila 101 Soviet Union Moscow Eye Mosfilmovsky Iberev Roku 12 Kwarchira 4 Soviet Union Moscow Satsvins Yanaberezhnaya 3 Kwarchila 82 Soviet Union Moscow Stavrobols Yauritsza 19ny Kwarchira 48 Procedural amendment (voluntary) November 10, 1988

Claims (5)

[Claims] (1) Bottom made from carbonaceous material (13, 21, 26
) and side parts (12, 20, 25), through-holes (14,
Quartz crucibles (1, 16, 19) used to grow crystals from melts with
, 24) to strengthen the shell (2, 15, 18, 2
3), wherein at least one portion (12, 20, 25 or 14, 21) of the shell (2, 15, 17, 23)
, 26), the carbonaceous material contains 10 to 150 pyrolyzable carbon.
% impregnated carbon fiber, characterized in that the ratio of the total area of the through holes to the external surface area of the crucible (1, 16, 19, 24) is from 0.15 to 0.98.
Said shell. (2) The shell according to claim 1, characterized in that it can be accommodated inside the body of the quartz crucible (1, 11, 16, 19, 24). (3) Item 1 above, wherein the area of one hole (22) is equal to the area of a square whose side is 1 to 20 times the thickness (L) of the side wall of the crucible (19). shell by. (4) The wall thickness (K) of the side portion (25) of the shell is 01 to 2.5 times the wall thickness (l) of the crucible (24). Shell by term. (5) The shell according to item 3 above, characterized in that the wall thickness (m) of the bottom (26) of the shell is 1 to 5 times the wall thickness (l) of the crucible (24). .