JPH05306191A - Production of silicon single crystal - Google Patents

Abstract

PURPOSE:To suppress the generation of microdefects in the silicon single crystal and to effectively prevent the generation of OSF. CONSTITUTION:The pressure in a pulling up chamber is set at <=500mbar by using the device for producing the silicon single crystal by a Czochralski method constituted to provide a cylinder for coaxially enclosing a pulling up single crystal rod and to introduce a protective gas into this cylinder. In addition, the single crystal rod is pulled up and grown by setting the flow rate per unit area of the protective gas in the cylinder at >=0.251/min.cm<2> in the state of pulling up the single crystal rod. The single crystal rod with which the growth is completed is then held for at least 90 minutes in an atmosphere region kept at 50 to 300 deg.C.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a silicon single crystal ingot which can suppress the generation of minute defects such as swirl when manufacturing a silicon single crystal by the Czochralski method and can prevent and suppress the generation of OSF. The present invention relates to a manufacturing method of.

[0002]

2. Description of the Related Art Explaining the case of manufacturing a silicon single crystal ingot by the Czochralski method, a quartz crucible held by a graphite susceptor is provided at approximately the center of a pulling chamber (metal chamber) and the center of the bottom of the graphite susceptor Is supported from below by a support shaft that can be rotated and moved up and down. Raw material polycrystal silicon is loaded into a quartz crucible, and the polycrystal silicon is heated and melted by a graphite heater surrounded by a heat insulator to form a melt.
There is an opening in the center of the ceiling of the pulling chamber, and a rotating / upward / downward pulling shaft holding a seed crystal at the tip is lowered through a subchamber connected to this, and after immersion in the melt By pulling the seed crystal while rotating the pulling shaft and the quartz crucible, a single crystal rod 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 and discharged from the discharge port at the lower part of the pulling chamber.

The protective gas introduced has an extremely high purity, but contains SiO vapor generated by the reaction between the quartz crucible and the silicon melt in the pulling chamber. Most of the SiO vapor is discharged to the outside of the pulling chamber through the discharge port, but some of it is deposited as amorphous aggregates on the upper edge of the quartz crucible and the pulling chamber inner wall. This is guided by the turbulent flow generated in the pulled single crystal rod and around the surface of the melt, and it falls near the interface between the single crystal rod and the melt and causes dislocation and polycrystallization of the single crystal rod. Was there.

Further, stored oxygen and water contained in materials such as a graphite susceptor, a graphite heater and a heat retaining body (graphite felt) and which cannot be removed even by air reaction react with these carbonaceous materials heated to a high temperature. To produce CO and CO ₂ gas,
Concentration of impurities such as carbon in the single-crystal silicon rod with the impurity gas staying in the pulling chamber due to insufficient exhaust gas displacement in the pulling chamber and being brought into reflux contact with the surface of the melt due to the turbulent flow. It has been a cause of deteriorating the characteristics of the integrated circuit element of the wafer made from this single crystal ingot.

When forming integrated circuit elements at a high density on a silicon single crystal substrate, an OSF (Oxidation Induced Stacking Fau) is formed on the substrate surface by a thermal oxidation process.
lt: Below OSF) Swirl Defect
Other micro-defects are easily formed, which deteriorates the characteristics of electronic circuit elements and significantly reduces the product yield. However, in the production of single crystals by the conventional Czochralski method, the occurrence of these defects is suppressed. Was difficult.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the prior art. A cylinder surrounding a pulling single crystal rod coaxially is provided and a protective gas is introduced into the cylinder. The pressure inside the pulling chamber is adjusted to 50
By setting the flow rate per unit area of the protective gas to 0.25 l / min · cm ² or more, the single crystal ingot is pulled up and grown, and the predetermined heat treatment is applied to the completed single crystal ingot. It is an object of the present invention to provide a method for producing a silicon single crystal, which can suppress the generation of minute defects inside the single crystal and can effectively suppress the generation of OSF.

[0007]

In order to solve the above problems, in the method for producing a silicon single crystal of the present invention, a cylinder surrounding a pulling single crystal rod coaxially is provided and a protective gas is provided in the cylinder. Using the apparatus for producing a silicon single crystal by the Czochralski method, the pressure in the pulling chamber is set to 500 mbar or less, and the flow rate of the protective gas in the cylinder per unit area is set to the single crystal rod drawing. In the above state, the single crystal ingot is pulled up and grown at 0.25 l / min · cm ² or more, and the single crystal ingot which has completed the growth is immediately heated to 50 to 300 ° C. for at least 90 ° C. in the ambient temperature range.
It is designed to hold minutes.

The pressure inside the pulling chamber is 500
It is necessary to set it to mbar or less, preferably 100 to 150 mbar, and if it exceeds 500 mbar, it is impossible to suppress minute defects and the object of the present invention cannot be achieved.

The flow rate of the above protective gas per unit area is 0.25 l / min · cm ² or more when the single crystal rod is pulled up,
It is necessary to set it to preferably 0.25 to 1.00 l / min · cm ^2, and if it is less than 0.25 l / min · cm ² , it is still impossible to suppress the minute defects. Cannot be achieved.

The flow rate of the protective gas in the cylinder is 0.2
As a means for increasing the flow rate to 5 l / min · cm ² or more, the inner diameter of the conventional cylinder is narrowed so that the absolute flow rate of the protective gas is the same as the conventional one, or the conventional cylinder is used as it is and the absolute flow rate of the protective gas is increased. Good.

[0011]

In order to carry out the pulling up work according to the method of the present invention, the raw material polycrystalline silicon is charged in the quartz crucible as in the conventional case,
The pulling chamber is evacuated, the protective gas is introduced through the inlet, and is discharged through the outlet to replace the inside of the pulling chamber with the protective gas atmosphere. At this time, the pressure in the pulling chamber is set to 500 mbar or less. Then, a predetermined current is applied to the graphite heater to heat the raw material to form a melt, and then the pulling shaft is lowered and the seed crystal held at its lower end is once immersed in the melt, and its supporting shaft and pulling shaft are rotated. However, when the seed crystal is pulled up, a single crystal rod grows at the lower end thereof.

In the process of growing this single crystal, according to the present invention, the flow rate of the protective gas in the cylinder is 0.25 l / min.c.
Since it is defined as m ² or more, it is possible to effectively suppress the minute defects inside the single crystal and further effectively suppress the generation of OSF.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An example of an apparatus used in the method of the present invention will be described below with reference to the accompanying drawings. In FIG. 1, 2 is an apparatus for producing a silicon single crystal according to the present invention, in which a quartz crucible 8 held by a graphite susceptor 6 is provided in the center of a pulling chamber 4. The graphite susceptor 6 is supported from below by a support shaft 10 which is rotatable around the center of the bottom and is vertically movable. The pull-up chamber 4 has an opening 12 at the center of the ceiling, and the sub-chamber 1
A pull-up shaft 16 that can rotate and move up and down is provided in the unit 4. At the edge of the opening 12, a cylinder 20 is provided, one end of which is hermetically coupled and the other end of which is suspended toward the melt 18.
A collar 21 is formed at the lower end of the cylinder 20 and is folded back and spreads outward and upward. The collar 21 is not an essential component and may not be attached.

A protective gas inlet 22 is provided above the sub chamber 14, and an outlet 24 is opened at the bottom of the pulling chamber 4. In addition, 25 is an observation window provided in the upper part of the pulling chamber 4, H is a graphite heater, and K is a heat retaining body.

The characteristic structure of the apparatus shown in FIG.
The inner diameter of 0 is narrower than the inner diameter of the cylinder of the conventional device. In the illustrated example, the wall thickness of the side wall of the cylinder 20 is made thicker than in the conventional case, and the inner diameter of the cylinder is narrowed. The means for narrowing the inner diameter of the cylinder 20 is not limited to the illustrated example, and it is of course possible to manufacture the cylinder 20 with a small diameter from the beginning.

The reason for narrowing the inner diameter of the cylinder 20 is as follows.
The flow rate of the protective gas in the cylinder is easily 0.25 l / min.
in order to cm ² or more, but the inner diameter of the cylinder 20, it is also possible to increase the absolute flow rate of the protective gas without narrowing the same as conventional.

The operation of pulling the single crystal with the above-mentioned structure will be described. First, the quartz crucible 8 is loaded with polycrystalline silicon as a raw material, the pulling chamber 4 is evacuated, and a protective gas is introduced into the inlet 22.
It is further introduced and discharged from the discharge port 24 to replace the inside of the pulling chamber with a protective gas atmosphere. At this time, the pressure in the pulling chamber is 500
mbar or less. Then, a predetermined current is passed through the graphite heater H to heat the raw material to form the melt 18, and then the pulling shaft 16
The seed crystal S held at the lower end of the melt 18
When the seed crystal S is pulled up while being dipped in, and the supporting shaft 10 and the pulling shaft 16 are rotated, a single crystal rod G grows at the lower end thereof.

In the process of growing this single crystal, according to the present invention, the flow rate of the protective gas in the cylinder is 0.25 l / min · c.
Since it is defined as m ² or more, it is possible to effectively suppress the minute defects inside the single crystal and further effectively suppress the generation of OSF.

The method of the present invention will be further described below with reference to examples. Example 1 Using the apparatus shown in FIG.
0 mbar, flow rate of protective gas in the cylinder 0.4 l / min
A 6-inch φ, N-type <100> single crystal ingot was pulled up at a pulling rate of 1.2 mm / min under the condition of cm ² .

The grown ingot was immediately rolled up in the subchamber. The cooling pattern of the ingot at this time is shown in FIG. That is, the film was wound in an atmosphere temperature region of about 270 ° C. and held for 90 minutes. In FIG. 2, the atmospheric temperature in the chamber is shown by measuring the temperature of the atmospheric region corresponding to the central portion of the ingot.

A single crystal ingot was sliced to a thickness of 2 mm, and this was sliced from 800 ° C. to 1200 ° C. with a temperature gradient of 10 ° C. /
The temperature was raised at min, the temperature was maintained at 1200 ° C. in the wetO ₂ state for 100 minutes, and then the temperature gradient was 1.5 ° C./min.
The temperature was lowered to 800 ° C. After that, the oxide film was removed with hydrofluoric acid, and immersed in a seco-etching solution for 2 minutes to perform seco-etching, and the OSF density was measured with an optical microscope. From the result of FIG. 3, it was confirmed that the generation of OSF was suppressed.

The swirl 29 was observed by the following treatment. That is, a slice is cut out from the rolled single crystal ingot, and the slice is cut at 800 ° C to 1000 ° C.
The temperature is raised to 65 ° C. under wetO ₂ condition at 1000 ° C.
Hold for a minute and then cool to 800 ° C. After that, the oxide film was removed with hydrofluoric acid, Secco etching was performed in the Secco etching solution for 15 minutes while stirring, and the swirl 29 was observed with an optical microscope. It was found that the swirl 29 was moving in the outer peripheral direction as shown in FIG.

Comparative Example 1 An ingot pulled up after completion of growth is kept for a certain time (90
Min) After stopping, it was wound up in the sub-chamber. The cooling pattern of the ingot at this time is shown in FIG. 2 together with the first embodiment. That is, the atmospheric temperature in the chamber immediately after pulling up is 7
Hold at 00 ° C for 90 minutes. Except for the cooling pattern described above, the same treatment as in Example 1 was performed to measure the OSF density,
This is shown in FIG. 3 together with Example 1. From the result of FIG. 3, it was confirmed that high-density OSFs were generated.

When a slice was cut out from the rolled-up single crystal ingot and observed by an optical microscope in the same manner as in Example 1, the presence of the swirl 29 was observed.
It was confirmed that it exists inside the ingot as shown in.

Comparative Example 2 An ingot pulled up after completion of growth was 2 mm / min.
It was wound into the sub-chamber at the upper shaft speed. The cooling pattern of the ingot at this time is shown in FIG. 2 together with Example 1 and Comparative Example 1. That is, the ambient temperature in the chamber immediately after pulling up was 700 ° C. and was gradually cooled to 400 ° C. over 90 minutes.

Example 1 except for the above cooling pattern
The same process as in Example 1 was performed, the OSF density was measured, and the results are shown in FIG. From the result of FIG. 3, it was confirmed that high-density OSFs were generated.

Comparative Example 3 The OSF density was measured in the same manner as in Example 1 except that the flow rate of the protective gas in the cylinder was 0.2 l / min · cm ^2, and the results are shown in FIG. From the result of FIG. 6, it was confirmed that OSF was generated.

Comparative Example 4 The OSF density was measured in the same manner as in Comparative Example 1 except that the flow rate of the protective gas in the cylinder was changed to 0.2 l / min · cm ^2, and the results are shown in FIG. From the result of FIG. 6, high-density OSF
Could be confirmed.

Comparative Example 5 The OSF density was measured in the same manner as in Comparative Example 2 except that the flow rate of the protective gas in the cylinder was 0.2 l / min · cm ^2, and the results are shown in FIG. From the result of FIG. 6, high-density OSF
Was confirmed to occur.

[0030]

As described above, according to the present invention, a cylinder in which a pulling single crystal rod is coaxially surrounded is provided, and a protective gas is introduced into the cylinder. The pressure in the pulling chamber is 500 mbar or less. And the flow rate of the protective gas per unit area is 0.25 l / min · cm ² or more, the single crystal rod is pulled up and grown, and a predetermined heat treatment is applied to the grown single crystal rod to obtain a single crystal. It is possible to suppress the generation of internal minute defects and further effectively suppress the generation of OSF.

[Brief description of drawings]

FIG. 1 is a schematic longitudinal cross-sectional view showing an embodiment of an apparatus used in the method of the present invention.

FIG. 2 is a graph showing cooling patterns after completion of single crystal growth in Example 1 and Comparative Examples 1 and 2.

FIG. 3 is a graph showing the OSF generation status of Example 1 and Comparative Examples 1 and 2.

FIG. 4 is a graph showing a swirl generation position of the wafer of Example 1.

5 is a graph showing a swirl generation position on a wafer of Comparative Example 1. FIG.

FIG. 6 is a graph showing the OSF generation status of Comparative Examples 3 to 5.

[Explanation of symbols]

 2 Silicon Single Crystal Manufacturing Device 4 Pulling Up Chamber 6 Susceptor 8 Quartz Crucible 10 Support Shaft 12 Opening 14 Subchamber 16 Pulling Up Shaft 18 Melt 20 Cylinder 25 Observation Window H Heater

Claims (1)

[Claims] 1. An apparatus for producing a silicon single crystal by the Czochralski method, in which a cylinder surrounding a pulling single crystal rod coaxially is provided and a protective gas is introduced into the cylinder, and the pressure in the pulling chamber is used. Was set to 500 mbar or less, and the flow rate of the protective gas in the cylinder per unit area was set to 0.25 l / min · cm ² or more in the pulled-up state of the single crystal rod, and the single crystal rod was pulled up and grown to complete the growth. A method for producing a silicon single crystal, characterized in that the single crystal ingot is held in an atmosphere temperature region of 50 to 300 ° C. for at least 90 minutes immediately after completion of growth.