JPH0639351B2 - Apparatus and method for manufacturing single crystal ingot - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an apparatus and method for producing a single crystal ingot, and in particular, an apparatus for producing a high-purity silicon single crystal ingot having no stacking fault or microdefect with high production efficiency. And about the method.

(Prior Art and its Problems) Typical methods for producing high-purity single crystal ingots are the Czochralski method and the floating zone method, but the former is frequently used in the production of semiconductor integrated circuit elements.

A case where a silicon single crystal ingot is manufactured by the Czochralski method will be described with reference to FIG. 3, in which a quartz crucible 3 held by a graphite susceptor 2 is provided at approximately the center of a pulling chamber (metal chamber) 1. The center of the bottom portion of the susceptor is supported from below by a support shaft 4 which is rotatable and vertically movable. The raw material polycrystalline silicon was loaded into the quartz crucible, and this was used as the heat insulator 5.
The graphite heater 6 surrounded by is heated and melted to form a melt 7. There is an opening 8 in the center of the ceiling of the pulling room 1,
The sub-chamber 9 connected to this is passed through the sub-chamber 9, and the rotating and vertically movable pulling shaft 11 holding the seed crystal 10 at its tip is lowered,
When the seed crystal is pulled up while being rotated in the pulling shaft 11 and the quartz crucible 3 after being immersed in the melt 7, the single crystal ingot 12 can be grown under the seed crystal. During this time, a protective gas such as argon gas is introduced from the upper part of the sub-chamber 9, and 13 → 13 ′,
It is discharged from the discharge port 15 through the flow path indicated by 14 → 14 ′.

The protective gas to be introduced has an extremely high purity, but contains SiO vapor generated by the reaction between the quartz crucible 3 and the silicon melt 7 in the pulling chamber. Most of this SiO vapor is in the flow path 13
→ 13 ', 14 → 14' is discharged to the outside of the pulling chamber, but some of them adhere to the upper edge of the quartz crucible and the pulling chamber inner wall as amorphous aggregates 16 and 17, respectively. This causes turbulent flow 18, 18 'generated around the single crystal rod 12 that is pulled up and around the melt surface.
Led to near the interface between the single crystal rod and the melt, causing dislocation and polycrystallization of the single crystal rod.

In addition, the stored oxygen and water contained in the materials such as the graphite susceptor 2, the graphite heater 6, and the heat retaining body 5 (graphite felt) and could not be removed even by the air baking react with these carbonaceous materials heated to a high temperature. To generate CO or CO ₂ gas, which is led to the turbulent flows 18 and 18 ′ and refluxed to the surface of the melt together with the impurity gas remaining in the pulling chamber due to insufficient exhaust gas replacement in the pulling chamber. The contact with each other increases the concentration of impurities such as carbon in the single crystal silicon rod, which causes the deterioration of the characteristics of the integrated circuit element of the wafer made from this single crystal rod. Due to recent technological advances, carbon contamination of single crystal rods has been significantly reduced, but it is not always satisfactory.
In some cases, 0.1 to 0.3 ppma contamination may occur.

The pulling rate of the single crystal rod 12 must be adjusted by the temperature gradient of the single crystal rod at the solid-liquid interface, and this temperature gradient is influenced by the radiation heat from the graphite susceptor 2, the quartz crucible 3, the melt 7, etc. Receive big. Further, if the diameter of the pulling single crystal ingot increases, the pulling speed must decrease. This speed is usually 1.0 mm / min for a 4 ″ φ single crystal rod, but 0.8 mm / min for a 6 ″ φ, although it varies depending on the equipment and manufacturing conditions.

When forming high density integrated circuit devices on a silicon single crystal substrate, oxidation-induced defects (Oxida
tion Induced Stacking Fault (hereinafter referred to as OISF),
Swirl Defects and other small defects are easily formed, which deteriorates the characteristics of electronic circuit elements and significantly lowers the product yield.However, in the conventional Czochralski method device, these defects are generated. It was difficult to control.

In order to solve such problems, the following proposals have hitherto been made.

Japanese Patent Publication No. 51-47153.

To this end, a single crystal rod being pulled is surrounded, a heat shield ring is arranged above the melt, and this is moved up and down with respect to the single crystal rod to adjust the temperature gradient of the single crystal rod, and to establish a solid-liquid interface. Although it is described that a single crystal ingot having no crystal defects such as dislocation can be pulled up by planarization, no countermeasure against foreign matter or impurities is described therein.

Japanese Patent Publication No. 54-6511.

For this, a tube surrounding the single crystal rod is provided, atmospheric gas is introduced into the gap between the rod and the tube, and the spraying effect prevents SiO from precipitating and scattering in the pulling system of the single crystal rod. Although it is described, no countermeasure is taken for the occurrence of crystal defects due to carbon impurities, OISF and other pulling conditions.

JP-B-57-40119 discloses that the quartz crucible and the melt are partially covered by a cover member composed of a flat annular rim and a connecting part attached to the rim, but it is complicated as a practical problem. The cover member, which has a simple structure and covers the entire surface of the melt, is easily damaged by high temperature, and there is a risk of impurities being mixed into the product.

In addition to the above, various studies have been conducted in order to prevent the generation of minute defects such as OISF on the silicon surface after thermal oxidation. The cause of this generation is the small mechanical strain of the silicon substrate surface or the point defects generated during the heat treatment process. Agglomeration or sodium,
It was found to be surface contamination with aluminum or iron. Furthermore, in recent research, attention has been paid to so-called minute defects caused by oxygen in the silicon substrate, and the out-diffusion at high temperature intentionally creates an oxygen-deficient layer on the surface of the silicon substrate during thermal oxidation to produce an integrated circuit device manufacturing technology. Was developed. Further, as a result of investigating the cause of stacking fault occurrence due to such thermal oxidation, the stacking fault occurrence during thermal oxidation can be significantly reduced by the improvement of the heat treatment technique mainly based on the out-diffusion of oxygen contained in the wafer. It became so. However, as the density of integrated circuit devices has increased in recent years, it has been required to further reduce the stacking fault density to substantially zero.

(Means for Solving Problems) Based on such a background, the present invention has examined the pulling conditions of a single crystal ingot, and in particular, the temperature and cooling of each process in which a melt of silicon polycrystal is single crystallized and further cooled. We have found that adjusting the speed is effective in reducing OISF and swirl defects.

The present invention to make such an improvement, in addition to the graphite cylinder surrounding the single crystal rod being pulled, a collar is provided at the lower end thereof,
By appropriately adjusting the height and spread angle, it is possible to effectively block the radiant heat received by the single crystal rod from the melt and the graphite heater, and control the heat history during pulling the single crystal rod in a wide range. To

Another effect of the present invention is to prevent the carbon contamination of the pulled single crystal rod and the decrease in the single crystallization rate due to the drop of SiO on the surface of the silicon melt, which is a problem in the conventional method, and compared with the conventional method.
High-speed pulling of 50-100% or more is possible and extremely efficient production can be performed. That is, the first aspect of the invention is as follows: 1) In the apparatus for producing a single crystal rod by the Czochralski method, a cylinder that coaxially surrounds the pulling single crystal rod is provided, and one end of the cylinder has an opening in the center of the pulling chamber ceiling. A gist of an apparatus for manufacturing a single crystal rod is characterized in that it has a collar that is airtightly bonded to an edge and that the other end hangs down toward the surface of the melt in the quartz crucible and folds back upward and expands. In this case, 2) the distance between the lower end of the cylinder and the surface of the melt is 5 to 50 mm,
The gap between the cylinder and the pulled single crystal rod is 5 to 100 mm, and the shortest distance between the outer surface of the collar and either the inner wall or the upper end of the quartz crucible is 5 to 100 mm, 3) the collar and the cylinder are mutually It is characterized by being removable.

Further, the second invention is 4) coaxially surrounding a pulling single crystal rod, one end of which is hermetically coupled to an opening edge in the center of the pulling chamber ceiling, and the other end of which is hung toward the surface of the melt in the quartz crucible. Using a Czochralski method for producing single crystal rods, which is provided with a cylinder having a collar that is folded back upward and outward, it is possible to produce single crystal rods at a pulling rate of 1.1 mm / min or more. The gist is a method for producing a characteristic single crystal ingot, in which case 5) the distance between the lower end of the cylinder and the melt surface is 5 to 50 mm,
The gap between the cylinder and the pulled single crystal rod is 5 to 100 mm, and the shortest distance between the outer surface of the collar and either the inner wall or the upper end of the quartz crucible is 5 to 100 mm.

(Operation) The apparatus and method of the present invention will be described below with reference to the drawings.

FIG. 1 shows an apparatus according to an embodiment of the present invention, in which a quartz crucible 3 held by a graphite susceptor 2 is provided in the center of a pulling chamber 1 , and the graphite susceptor is rotated around the center of the bottom by a support shaft 4 which is vertically movable. It is supported from below. The pull-up chamber has an opening 8 in the center of the ceiling, the sub-chamber 9 is connected to the pull-up chamber, and the pull-up shaft 11 that is rotatable and vertically movable is provided in the sub-chamber.
A cylinder 19 is provided at the edge of the opening 8 so that one end is airtightly coupled and the other end is hung down toward the melt. A collar 20 is formed at this other end and is folded back and spreads outward and upward. There is. A protective gas inlet 21 is opened above the sub chamber, and an outlet 15 is opened at the bottom of the pulling chamber.

The connection between the upper end of the cylinder 19 and the edge of the opening 8 does not necessarily require a high degree of airtightness, and the protective gas introduced into the cylinder may leak to some extent.

Next, the configuration and operational effects of the above device of the present invention will be described.

First, the raw material polycrystalline silicon is loaded into the quartz crucible 3, the pulling chamber 1 is evacuated, the protective gas is introduced through the inlet 21, and the outlet 15 is discharged to replace the inside of the pulling chamber with the protective gas atmosphere. Then, a predetermined current is applied to the graphite heater 6 to heat the raw material to form a melt 7, and then the pulling shaft 11 is lowered and the seed crystal 10 held at the lower end thereof is once dipped in the melt 7 and the supporting shaft 4 is pulled. When the seed crystal 10 is pulled up while rotating the upper shaft 11, the single crystal rod 12 grows at the lower end thereof.

The temperature of the single crystal rod during pulling is determined by indirect radiant heating through the cylinder, except for heat conduction from the solidification interface, so to increase the cooling rate of the single crystal rod during pulling,
It is necessary that the collar block direct radiation from the melt, heater and graphite susceptor to the cylinder, and it is desirable that the collar and cylinder are not in close proximity.

For this reason, the geometrical dimensions of the collar must be set as follows.

For example, if the collar is a hollow truncated inverted conical shape that expands immediately upward and outward from the lower end of the cylinder with a straight line inclined by an angle α from the vertical line as a generatrix, then an angle α of 0 to 90 ° is effective, More preferably, it is about 15 to 70 °.

When the angle α is 15 to 70 °, the heat shielding effect on the cylinder and by extension the single crystal rod is large, cooling in the center of the pulling chamber of the single crystal rod during pulling is promoted, and the single crystal rod is rapidly cooled, Since trace impurities contained in the crystal, particularly oxygen, are dispersed and fixed in a substantially dissolved state, the generation of microdefects is greatly suppressed, and in particular, a single crystal rod free from OISF and swirl defects can be grown. As a result, in the integrated circuit device manufacturing process, a low temperature, for example, 600 to 800, is formed due to formation of a denuded zone and intrinsic gettering.
It is no longer necessary to perform both pre-treatment at ℃ and high temperature such as 1100 to 1200 ℃.
The advantage of being able to simultaneously form the denuded zone and the intrinsic gettering is obtained with only this.

When the angle α is smaller than 15 ° or larger than 70 °, the temperature of the cylinder rises and the radiant heat from the cylinder becomes stronger than when the angle α is in the range of 15 to 70 °. It becomes difficult for the single crystal rod to be cooled.

When the angle α is smaller than 15 °, of course, the radiant heat from the surface of the silicon melt, the graphite susceptor and the heater can be blocked by the collar, but the temperature of the cylinder rises due to the proximity of the collar and the cylinder, It becomes difficult to cool the single crystal ingot.

Cooling of the single crystal rod during pulling is performed by heat conduction through the seed crystal at the upper end of the single crystal rod and heat exchange with the surface of the single crystal rod of the protective gas flowing downward in the cylinder, but the radiation heat from the cylinder is large. Therefore, it becomes difficult to cool the single crystal rod during pulling.

If the angle α exceeds 70 °, direct radiation from a part of the surface of the silicon melt, the graphite susceptor and the heater is given to the cylinder, resulting in the same thermal effect as when the angle is small. It occurs in the single crystal rod inside and it becomes difficult to cool it sufficiently.

In the above cases, the numerical value of α was distinguished by 15 ° or 70 °, but the diameter of the pulled single crystal rod, the diameter of the cylinder used,
There is some variation depending on the distance of the tip from the melt, the inner diameter of the quartz crucible to be used, and the depth of the melt from the upper end of the quartz crucible. the value of α is
If the temperature is outside the range of 15 to 70 °, or if it is within the range of 15 to 70 ° and is close to the upper and lower limits on both sides, the cooling rate at the center of the pulled single crystal rod becomes slow and the single crystal rod is pulled up. A silicon substrate obtained from such a single crystal rod in which microdefects grow can have a high getter effect, that is, an intrinsic gettering effect due to the microdefect.

Even if α is 15 to 70 °, the intentional growth of such microdefects can be achieved by reducing the gap between the single crystal rod and the cylinder to limit the cooling effect of the single crystal rod. realizable. Also, when the value of α is smaller than 15 ° and larger than 70 °, the occurrence of OISF and swirl defects is sufficiently suppressed, and a high temperature such as 1200 ° C is selected in the first heat treatment step of the integrated circuit device manufacturing process. Thereby, the denuded zone which can endure practical use can be formed.

In the present invention, in order to enhance the heat shield effect of the collar, it is necessary to adjust the angle α and select an appropriate height and diameter, but the height of the collar is not particularly limited, but the length of the cylinder is It cannot be exceeded.

Further, the combination of the cylinder and the collar of the present invention can obtain the following other effect.

The space formed by the collar, the inner wall of the quartz crucible and the surface of the silicon melt held in the quartz crucible is significantly limited as compared with the case without the collar, so that the space on the surface of the silicon melt is significantly limited. When the protective gas introduced through the gap between the single crystal rod and the argon gas reaches the surface of the silicon melt and then reverses and is discharged to the outside of the quartz crucible, the residence time on the surface of the silicon melt. Is limited to a short time, flows through the narrow gap between the inner wall of the quartz crucible and the upper edge of the collar at a relatively high speed, and flows like washing the inner wall of the quartz crucible and / or the upper edge of the collar. There was no aggregation of SiO evaporated from the silicon melt on the upper edge of the quartz crucible,
In addition, the carbon susceptor in the pull-up chamber, the heater, and the carbon or CO ₂ originating from the graphite heat insulator surrounding them do not flow back to contaminate the silicon melt with carbon.

The shape and size of the collar to prevent carbon contamination and agglomeration of SiO on the inner wall and upper edge of the quartz crucible as described above limit the protective gas on the surface of the silicon melt, so that the collar and the surface of the silicon melt and the quartz The space between the inner wall of the crucible and the inner wall of the quartz crucible is limited to a closed space.
It is desirable to design the collar so that it is located between them and attach it to the lower end of the cylinder. During the pulling process, when the collar is completely inside the quartz crucible, for example when it is a hollow truncated cone, the maximum outer diameter of the upper end of the collar and the inner wall of the quartz crucible are 5 Adjust to ~ 100mm.

Next, in the present invention, the pulling speed of the single crystal rod is OISF.
It is necessary to speed up to prevent occurrence and improve productivity. Depending on the diameter of the pulled single crystal rod and the pulling conditions, the speed is
If the speed is 1.0 mm / min or less, OISF and swirl defects occur frequently, so the speed is preferably 1.0 mm / min or more.

To achieve high-speed pulling, it is necessary to increase the temperature gradient in the growth axis direction on the solid-liquid interface between the silicon melt and the growing silicon single crystal ingot, that is, on the solid side of the growth interface. , The gap between the cylinder and the single crystal rod,
It was experimentally confirmed that it is necessary to limit the distance to a certain range and the distance between the lower end of the cylinder and the surface of the silicon melt to a certain value. That is, the gap between the inner diameter of the cylinder and the pulled single crystal ingot is 5 to 100 mm, and the distance between the tip of the cylinder and the surface of the silicon melt is preferably limited to 5 to 50 mm. If the gap between the cylinder and the single crystal rod is 5 mm or less, the pulling single crystal rod may make a slight eccentric movement during pulling to contact the inner wall of the cylinder, or may contact due to poor control of the diameter of the pulling single crystal rod. In the sense of avoiding these, if the gap becomes too small, the distribution of the gas flow becomes non-uniform, and the gas flow in the space between the outer surface of the collar and the surface of the silicon melt and the inner wall of the quartz crucible becomes non-uniform. It means to prevent. In addition, the gap between the diameter of the single crystal rod and the inner diameter of the cylinder is 10
If it exceeds 0 mm, the flow velocity of the protective gas flowing through this gap decreases, the cooling effect of the protective gas decreases, and the protective gas is wasted. Next, when the lower end of the cylinder is close to the surface of the silicon melt by 5 mm or less, vibration occurs due to the gas flow on the surface of the silicon melt, which adversely affects single crystallization. It becomes insufficient and it becomes impossible to pull up at high speed.

In short, the present invention provides each dimension of the cylinder, that is, the gap between the pulled single crystal rod and the cylinder is 5 to 100 mm, and the tip of the cylinder is 5 to 50 mm with respect to the surface of the silicon melt (for this purpose, usually silicon is used). The surface of the melt is at a certain distance from the bottom of the cylinder, and the quartz crucible is raised automatically or manually in conjunction with the pulling process of the single crystal rod.) , For example, in the case of a hollow truncated cone, the angle α from the vertical line is 0 to 90
By adjusting the minimum clearance between the outer surface of the collar and either the inner wall of the quartz crucible or the upper edge to be 5 to 100 mm, the pulling speed of the single crystal rod is 50 to 100 compared to the conventional method.
%, It is possible to increase the pulling speed to 1.0 mm /
By keeping the amount at least, it is possible to substantially eliminate the occurrence of OISF, swirl defects, etc., which are not preferable in manufacturing a semiconductor device. Also, carbon contamination of silicon single crystal rods is negligibly small, for example, a measurement limit of 0.05 pp.
Below ma, it is possible to prevent the generation of amorphous agglomerates of SiO adhering to the upper edge of the quartz crucible, which is often a problem in the conventional method, and the disorder of the single crystal rod due to the drop can be substantially reduced to zero.

In addition to the straight line of the busbar as shown in Fig. 1, the collar is composed of curved lines as shown in Fig. 2 (a) and the lower end of the cylinder as shown in Fig. 2 (b). Can be tapered to enhance the heat shielding effect and the gas cooling effect for the single crystal ingot.

22 shown in FIG. 1 is a window for observing the single crystal rod being pulled,
Further, by providing the window 23 in the cylinder as shown in FIGS. 2 (c) and 2 (d), the appearance of the single crystal ingot immediately after being pulled can be observed.

Further, the materials for the collar and the cylinder can also be improved in durability as amorphous carbon, graphite, silicon nitride or graphite coated with silicon carbide, and the heat insulating effect can be further enhanced by a multilayer structure of these materials. Alternatively, it is possible to use a refractory metal material in consideration of preventing metal contamination of the single crystal rod.

Further, the collar 20 can be manufactured easily if it can be attached to and detached from the cylinder 19 with a screw or the like, and the collar, which easily wears out, can be replaced easily and economically.

(Example) A graphite cylinder having an inner diameter of 200 mm that hangs toward the surface of the melt in the crucible is airtightly joined to the edge of the opening 8 in the center of the ceiling of the pulling chamber of the present invention, and the tip of the cylinder is outwardly extended upward. Manufactured by the Czochralski method with the structural arrangement shown in Fig. 1, which is formed by a busbar with an inclination angle of 60 ° from the folded vertical line, has a maximum outer diameter of 360 mm, and is equipped with a graphite collar of the same material as the cylinder. An apparatus was used to pull and manufacture a silicon single crystal ingot.

The inner diameter of the quartz crucible is 460 mm, and 60 kg of high-purity polycrystalline silicon was loaded into this, and after heating and melting, 100% argon gas was added.
Introduced at a flow rate of 1 / min, the seed crystal is immersed in the melt while maintaining the support shaft 4 so that the lower end of the cylinder equipped with the collar is 30 mm above the surface of the melt, and 1.3 mm / min. The single crystal was pulled at a pulling rate to manufacture 10 silicon single crystal rods having a diameter of 160 mm and a straight body length of 1200 mm (the above is referred to as production A).

Next, in the conventional Czochralski method device shown in FIG. 3 which does not have a collared cylinder, the same shape is obtained under the same conditions as A except for the conventional manufacturing condition of a pulling speed of 0.9 mm / min. Six silicon single crystals were produced (the above is production B).

The following table shows the inspection results of both the A and B single crystal rods produced.

(Effects of the Invention) The present invention can improve the crystal quality of a pulled single crystal ingot by the method and apparatus as described above, prevent single crystal disorder, and further increase the pulling rate to increase the production efficiency, Moreover, the device has a simple structure and is easy to handle, and has extremely excellent industrial applicability.

[Brief description of drawings]

FIG. 1 is a longitudinal sectional view of the device of the present invention, and FIG. 2 is a view showing another embodiment of a cylinder and a collar of the device of the present invention.
(A) and (b) are vertical sectional views, and (c) and (d) are windows 23.
FIG. 3 is a perspective view of a cylinder and a collar provided with the above, and FIG. 3 is a longitudinal sectional view of a conventional Czochralski method apparatus. 1 ... pulling chamber, 2 ... graphite susceptor, 3 ... quartz crucible, 4 ... support shaft, 5 ... heat retaining body, 6 ... graphite heater, 7 ... melt, 8 ... opening, 9 ...... Subchamber, 10 …… Seed crystal, 11 …… Pulling shaft, 12 …… Single crystal rod, 13, 13 ', 14, 14' …… Flow path, 15 …… Discharge port, 16, 17 …… Amorphous aggregate, 18, 18 '... Turbulence, 19 ... Cylinder, 20 ... Color, 21 ... Inlet, 22 ... Observation window, 23 ... Window, α ... Angle.

Front page continuation (72) Inventor Tetsuhiro Oda 2-13-50 Kitafu, Takefu City, Fukui Prefecture Shinetsu Semiconductor Co., Ltd. Takefu Factory (72) Inventor Tokuhiko Mizuno 2-13-50 Kitafu, Takefu City, Fukui Prefecture Shinetsu Semiconductor Co., Ltd., Takefu Factory (72) Inventor Masami Nakano 2-13-1, Isobe, Annaka-shi, Gunma Shin-Etsu Semiconductor Co., Ltd. Semiconductor Research Laboratory (72) Inventor, Kei Uchikawa 2-13, Kitafu, Takefu City, Fukui Prefecture No.50 Shin-Etsu Semiconductor Co., Ltd., Takefu Factory (56) References JP-A-64-61383 (JP, A)

Claims (5)

[Claims] 1. A manufacturing apparatus for a single crystal rod by the Czochralski method, wherein a cylinder surrounding the pulling single crystal rod is provided coaxially, and one end thereof is airtightly coupled to an opening edge at the center of the pulling chamber ceiling,
An apparatus for producing a single crystal rod, characterized in that the other end has a collar that hangs toward the surface of the melt in the quartz crucible and folds back outward and expands. 2. The distance between the lower end of the cylinder and the surface of the melt is 5
~ 50 mm, the gap between the cylinder and the pulling single crystal rod is 5 ~ 100 mm
The apparatus for producing a single crystal ingot according to claim 1, wherein the shortest distance between the outer surface of the collar and either the inner wall or the upper end of the quartz crucible is 5 to 100 mm. 3. The apparatus for producing a single crystal ingot according to claim 1, wherein the collar and the cylinder are detachable from each other. 4. A pulling single crystal rod is coaxially surrounded, one end is airtightly coupled to an opening edge in the center of the pulling chamber ceiling, and the other end is hung toward the surface of the melt in the quartz crucible and folded back upward. Using the Czochralski method for producing single crystal rods with a cylinder having an expanded collar, a single crystal rod is
A method for producing a single crystal ingot, which is produced at a pulling rate of not less than / min. 5. The distance between the lower end of the cylinder and the surface of the melt is 5
~ 50 mm, the gap between the cylinder and the pulling single crystal rod is 5 ~ 100 mm
5. The method for producing a single crystal ingot according to claim 4, wherein the shortest distance between the outer surface of the collar and either the inner wall or the upper end of the quartz crucible is 5 to 100 mm.