JP2826589B2 - Single crystal silicon growing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for growing a silicon single crystal by the Czochralski method (hereinafter referred to as CZ method), and more particularly, to controlling the temperature distribution inside a single crystal during the growth thereof. The present invention relates to a single crystal growing method for controlling quality.

[0002]

2. Description of the Related Art There are various methods for producing a silicon single crystal used as a material for a highly integrated semiconductor device, but the CZ method is mainly employed as a method capable of industrial mass production. FIG. 3 shows an implementation state of the CZ method.

[0003] In the CZ method, a crucible 1 having a double structure composed of quartz on the inside and graphite on the outside is usually used. The raw silicon contained in the crucible 1 is heated and melted by the heater 2 disposed outside the crucible 1. The silicon melt 3 is gradually pulled up from the crucible 1 by raising the wire 5 attached to the seed crystal 4 at the lower end. At this time, the crucible 1 and the seed crystal 4 are rotated. As a result, a columnar single crystal 6 in which the silicon melt 3 is solidified is grown. Normally used crystal growth rate is 1.0-2.0mm / min
It is.

In growing a silicon single crystal by such a CZ method, it is known that a ring-shaped acid-induced stacking fault called an OSF ring is generated on the wafer surface by performing a heat treatment after processing the single crystal into a wafer. Have been.

When the OSF ring is generated, oxygen precipitates having high thermal stability grown during crystal growth are distributed at a high density of about 10 ⁶ cm ^-3 in the inner region, and the breakdown voltage characteristic of the gate oxide film is reduced. I do. On the other hand, in the region outside the OSF ring, the oxide withstand voltage characteristics are good, but the size is about 400 μm.
nm dislocation clusters are generated at a density of about 10 ³ / cm ² . As described above, the physical properties of the wafer are greatly different between the inside and the outside of the OSF ring.

A silicon single crystal manufactured by the CZ method is used for a highly integrated semiconductor device material. However, the reliability and the yield of the highly integrated semiconductor device strongly depend on the physical properties of the single crystal wafer. In growing a silicon single crystal, the position of the OSF ring is controlled and the O.S.
Generating an SF ring is an important technique.

In connection with this, the present inventors set the crystal growth rate to V (mm / min) and set the crystal growth rate to 1300 from the melting point of silicon.
The temperature gradient along the crystal axis in the temperature range up to
(° C./mm), it has been found that the position where the OSF ring is generated is uniquely determined by V / G (mm ² / ° C. · min), and according to Japanese Patent Application No. 6-148939, V / G is set to 2. 5 or more to generate an OSF ring on the outer peripheral portion of the wafer not used for device manufacture, and from 1150 ° C. to 100 ° C.
A single crystal production method was proposed in which the cooling rate in the temperature range up to 0 ° C. was 2.0 ° C./min or less and the distribution density of oxygen precipitates inside the OSF ring was reduced.

[0008]

In the single crystal manufacturing method proposed by the present inventors, it is important to control V / G with high precision in order to generate an OSF ring at a target position. Technology.

However, in growing a silicon single crystal by the CZ method, as shown in FIG.
While radiant heat from the single crystal 6 exists. Since the length of the single crystal 5 changes as the single crystal 5 grows, the axial distribution of the amount of heat radiated from the single crystal 6 changes every moment. Therefore, G is not kept constant during the growth of the single crystal 6. In order to control V / G, it is necessary to detect and operate not only V but also G. However, as described above, it is difficult to detect and operate V in actual operation.
The control of G is very difficult, and therefore O
It is not easy to generate an SF ring (see the conventional method in FIG. 2).

[0010] It is an object of the present invention to grow a single crystal silicon which can control V / G and thus the position where an OSF ring is generated with high accuracy by manipulating the temperature distribution inside the single crystal during growth as desired. It is to provide a method.

[0011]

According to the method for growing single crystal silicon of the present invention, when a silicon single crystal is manufactured by the CZ method, the temperature inside the single crystal is calculated by calculating the temperature distribution in the entire furnace using heat transfer calculation. The temperature distribution inside the single crystal is manipulated by obtaining a distribution and blocking and / or reflecting radiation from the melt using the obtained temperature distribution.

In the control of V / G, the temperature distribution of the entire furnace is calculated using heat transfer calculation, and the melting point of silicon is reduced by 130 ° C.
A temperature gradient G (° C./mm) in the crystal axis direction up to 0 ° C. is obtained,
The crystal growth rate V (mm / min) and the determined temperature gradient G (° C /
mm) is controlled so that the ratio V / G (mm ² / ° C. min) to the target value is controlled to a target value, and G is controlled by blocking and / or reflecting radiation from the melt.

Preferably, the temperature distribution calculation is corrected based on the measured temperature around the single crystal.

[0014]

In the control of V / G, it is indispensable to control the temperature gradient in the single crystal axis direction during the growth of the single crystal.
In this control technique, it is necessary to obtain the temperature distribution inside the single crystal during growth and to manipulate the temperature distribution. In terms of V / G control, it is necessary to both obtain G and operate G.

[0005] The temperature distribution inside the single crystal can be obtained by measuring the temperature around the single crystal at many points, but it is necessary to install many measuring instruments in the furnace. In addition, contamination of the single crystal grown in the furnace or in the furnace becomes a problem. Therefore, in the present invention, this is performed by calculating the temperature distribution of the entire inside of the furnace using the heat transfer calculation.

More specifically, the heat transfer calculation is performed by taking into consideration items such as radiant heat exchange in the entire furnace, the interface shape between the single crystal and the melt, the heater power, and the growth rate of the single crystal. The temperature distribution inside the crystal is determined, and G is determined in V / G control.

In this case, ie, in the radiant heat exchange in the entire furnace, in addition to the shape of the heat insulating material and the heat insulating material in the furnace and the length of the single crystal being grown, in the present invention, the radiation from the melt is cut off in the present invention. And reflections, it is necessary to consider the current position of obstacles and reflections. In addition, regarding the item, namely, the interface shape between the single crystal and the melt, the Stefan condition and the Boundry-fi
It can be obtained from the tted method.

According to the furnace temperature distribution calculation using the heat transfer calculation, the number of temperature measurement points can be reduced and the temperature distribution inside the single crystal can be obtained with high accuracy. Note that the temperature measurement in this case is not necessarily required because it is for correcting the temperature distribution calculation. When performing temperature measurement, it is preferable to measure the crystal surface temperature at a certain distance from the solid-liquid interface. However, in the present invention, in order to perform the temperature distribution calculation over the entire furnace, radiation cutoff responding to the single crystal temperature distribution The temperature of a specific position of an object or a heat insulating material may be measured.

Regarding the operation of the temperature distribution, the present invention blocks and / or reflects radiation from the melt. Since the temperature of the interface between the single crystal and the melt is constant, by blocking radiation from the melt to the single crystal and lowering the temperature of the single crystal,
The temperature gradient in the direction of the single crystal axis becomes large, and G can be increased in V / G control. On the other hand, by installing a high-reflectance reflector above the melt and reflecting radiation from the melt to the single crystal, the temperature of the single crystal increases and the temperature gradient in the single crystal axis direction decreases, In V / G control, G can be reduced. It is also possible to manipulate G using both blocking and reflection simultaneously.

Thus, V / G can be controlled with high accuracy, and an OSF ring can be generated at a target position.

[0011]

FIG. 1 shows an apparatus configuration suitable for carrying out the present invention.

In FIG. 1, reference numeral 7 denotes a cylindrical radiation shield provided above the crucible 2 so as to surround the pulling path of the single crystal 6. The radiation shield 7 is made of, for example, carbon and accommodates the single crystal 6 pulled up from the melt 3 in the crucible 1 and blocks radiation from the melt 3 to the single crystal 6. In addition, the radiation blocker 7 is moved up and down by the drive unit 8 in order to control the blocking amount.

Reference numeral 9 denotes a plurality of radiation reflectors arranged circumferentially so as to surround the hoistway of the radiation shield 7.
The radiation reflector 9 is, for example, a Mo plate having a mirror-polished surface, and reflects radiation from the melt 3 to the single crystal 6. Further, in order to control the amount of reflection, the angle of each radiation reflector 9 is adjusted by the drive unit 10.

Reference numeral 11 denotes a thermometer, which measures the temperature at a point at a certain distance from the solid-liquid interface on the surface of the single crystal 6.

Reference numeral 12 denotes G for determining a temperature gradient G in the crystal axis direction in a temperature range from the melting point of silicon to 1300 ° C.
It is an arithmetic unit. The G calculator 12 is provided with position information of the radiation blocker 7 from the drive unit 8. Further, the drive unit 10 gives angle information of the radiation reflector 9, and the thermometer 11 gives temperature information around the single crystal. Further, information on the shape of the heat insulating material and the heat insulating material in the furnace, the length and growth speed V of the single crystal 6 during growth, the interface shape between the single crystal 5 and the melt 3, and the power of the heater 2 are also given. Can be

The G calculator 12 calculates the temperature distribution of the entire furnace by heat transfer calculation using the information except for the measured temperature of the single crystal 6, and further calculates the temperature distribution using the measured temperature. G is obtained by performing the above correction.

Reference numeral 13 denotes a V / G controller. The V / G controller 13 calculates V / G from the obtained G and the single crystal growth rate V, and manipulates V so that the calculated value matches the V / G set value, and collects radiation. G is operated by instructing the driving units 8 and 10 on the position of the object 7 and the angle of the radiation reflection object 9. Also, the power of the heater 2 is operated as needed.

Thus, V / G is controlled to the set value over the entire period of single crystal growth. As a result, the OSF ring generated when the grown single crystal is processed into a wafer and the wafer is heat-treated is controlled to a predetermined position.

That is, certain assumptions (C _v ^ez , C _i ^ez , D
_v , constants of D _i ), but T / 1300 ° C. to 125
The concentration of point defects (vacancies and interstitial silicon) at 0 ° C. is substantially determined, and the point defects subsequently react with oxygen to generate oxygen precipitates of various sizes and densities or secondary defects (dislocations) thereof. Let it. Therefore, by controlling V / G to be constant, the position where the OSF ring is generated becomes constant over the entire crystal. Further, the distribution of defects such as oxygen precipitates (size-density distribution in the plane and in the axial direction) becomes constant.

However, the crystals are rapidly cooled when the tail part is formed at the end of the crystal growth and when the crystals are separated from the melt thereafter. At this time, since the Top side is rapidly cooled from a low temperature and the Tail side is rapidly cooled from a high temperature, these portions do not have a uniform defect distribution. For this reason, the position where the OSF ring is generated is not controlled in portions corresponding to the early and late stages of the growth. The non-uniform portion defect is a defect formed during crystal cooling at 100 to 850 ° C. or lower, and is a very small precipitate. On the other hand, defects formed at 1000 to 850 ° C. or higher are largely stable and uniform over the entire length of the crystal. Such a defect is stable even during the device process, and remains reliably in the device active region (near the surface), thus deteriorating the characteristics.

Next, V / G is actually measured using the apparatus shown in FIG.
Will be described.

Example 1 A quartz crucible having a diameter of 16 ″ was charged with 50 kg of high-purity polycrystalline silicon, doped with boron, and heated and melted with polycrystalline silicon.
single crystal with a crystal growth orientation of <100>
mm. During single crystal growth, the surface temperature of the crystal is measured with a radiation thermometer, and V / V is calculated with a single crystal temperature distribution calculation system.
Calculate G and V / G is 0.28 mm ² / ° C · min (constant)
In addition to controlling the growth rate of the single crystal, a cylindrical radiation reflector made of carbon having an inner diameter of 300 mm and a thickness of 30 mm disposed around the single crystal was moved up and down.

A sample was cut out of the grown single crystal in parallel to the crystal axis direction and heat-treated, and the position of the OSF ring was examined. The OSF ring was generated at a position of about 67 mm from the center except for a portion of 20 mm in the early stage of growth and a portion of 100 mm in the late stage of growth.

Example 2 A quartz crucible having a diameter of 16 ″ was charged with 50 kg of high-purity polycrystalline silicon, doped with boron, and melted by heating the polycrystalline silicon.
single crystal with a crystal growth orientation of <100>
mm. During single crystal growth, the surface temperature of the crystal is measured with a radiation thermometer, and V / V is calculated with a single crystal temperature distribution calculation system.
Calculate G and V / G is 0.22 mm ² / ° C · min (constant)
In addition to controlling the growth rate of the single crystal, the angle of five Mo plate radiation reflectors (one dimension is 250 mm x 150 mm), which are arranged around the single crystal and whose surface is polished to a mirror surface, is controlled. did.

A sample was cut out of the grown single crystal in parallel with the crystal axis direction and heat-treated, and the location of the OSF ring was examined. The OSF ring was formed at a position of about 15 mm from the center except for a portion of 20 mm in the early stage of growth and a portion of 100 mm in the late stage of growth.

Example 3 A quartz crucible having a diameter of 16 ″ was charged with 50 kg of high-purity polycrystalline silicon, doped with boron, and melted by heating the polycrystalline silicon.
single crystal with a crystal growth orientation of <100>
mm. During single crystal growth, the surface temperature of the crystal is measured with a radiation thermometer, and V / V is calculated with a single crystal temperature distribution calculation system.
Calculate G and calculate V / until the growth length of the single crystal is 500 mm.
G is 0.22mm ² / ℃ · min, as development length since 500mm becomes 0.28mm ² / ℃ · min, while operating the single crystal growth rate, location and Mo radiation reflection of the carbon radiation reflector The angle of the object was manipulated.

A sample was cut out of the grown single crystal in parallel with the crystal axis direction and heat-treated, and the position of the OSF ring was examined. The OSF ring is generated at a position of about 15 mm from the center in the portion from 20 mm to 450 mm, gradually moves to the outer periphery from 450 mm, and moves from the center to about 6 mm in the portion from 550 mm to 100 mm.
It occurred at a position of 7 mm.

FIG. 2 shows the position where the OSF ring is generated in each embodiment. Also, for comparison, the OSF ring occurrence position in the case of the conventional method in which V / G is not controlled is shown. As can be seen from the figure, the present invention enables high-precision control of V / G, and makes it possible to generate an OSF ring at a target position. By the way, the conventional method is three times from the center of the crystal.
In this case, crystal growth is performed with the aim of generating an OSF ring at a position of 5 mm, but the actual position where the OSF ring is generated is greatly deviated from the target position.

[0029]

As described above, the single crystal silicon growing method of the present invention determines the temperature gradient inside the single crystal by calculating the temperature distribution in the entire furnace using the heat transfer calculation, and obtains the radiation from the melt. By manipulating the temperature gradient inside the single crystal by blocking and / or reflection, it is possible to control V / G with high accuracy, thereby producing an effect that an OSF ring can be generated at a target position.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an apparatus suitable for carrying out the present invention.

FIG. 2 is a graph showing the effect of the present invention.

FIG. 3 is a schematic cross-sectional view showing an embodiment of a Czochralski method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Crucible 2 Heater 3 Melt 4 Seed crystal 5 Wire 6 Single crystal 7 Radiation blocker 9 Radiation reflector

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int. Cl. ⁶ , DB name) C30B 28/00-35/00 C30B 15/20-15/28

Claims (3)

(57) [Claims] When a silicon single crystal is produced by the Czochralski method, a temperature distribution inside the single crystal is obtained by calculating a temperature distribution in the whole furnace using heat transfer calculation, and melting is performed using the obtained temperature distribution. A method for growing single-crystal silicon, comprising controlling the temperature distribution inside a single crystal by blocking and / or reflecting radiation from a liquid. 2. A temperature gradient G (° C./mm) in a crystal axis direction from the melting point of silicon to 1300 ° C. is determined by calculating a temperature distribution of the entire inside of the furnace using heat transfer calculation.
(Mm / min) and the obtained temperature gradient G (° C./mm).
V (mm ² / ° C · min) is controlled to the target value so that V
2. The method of growing single-crystal silicon according to claim 1, wherein G is operated by blocking and / or reflecting radiation from the melt. 3. The method of growing a single crystal silicon according to claim 1, wherein the temperature distribution calculation is corrected based on a measured temperature around the single crystal.