JPS5954694A - Method for growth of single crystal - Google Patents

Abstract

PURPOSE:To obtain a right cylindrical single crystal having uniform diameter by the pulling of single crystal using Czochralskii method, by pulling the crystal while irradiating the meniscus line between the pulled crystal and the molten liquid with laser beam, and controlling the pulling speed at a constant level. CONSTITUTION:A single crystal is pulled and grown from the molten liquid 23 for the growth of crystal in the crucible 21 by Czochralski method using a seed crystal 24. In the above process, the growth is carried out under the irradiation of the laser beam 35 to the meniscus line 33 through the quartz inspection window 31 to suppress the abnormal growth and to melt the laterally grown excessive single crystal. The pulling speed of the crystal is adjusted to somewhat lower than the standard level to obtain a rather large crystal and keep only an extremely small part of the crystal always to molten state by irradiation with the laser beam.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Technical Field of the Invention The present invention relates to a single crystal growth method, and particularly to a growth method that can suppress the growth of abnormal crystals and obtain a single crystal bulk having a uniform diameter.

(b) Technical background JC, semiconductor devices such as transistors are silicon (Si)
), gallium arsenide (GaAs), etc., using single crystal substrates (wafers), but these single crystals are formed using the Czochralski method (abbreviated as CZ method) or the floating zone method (abbreviated as FZ method). It is made.

The CZ method is characterized by its large diameter, and the FZ method is characterized by the fact that it is easy to obtain highly pure crystals, but currently single crystals obtained by the CZ method are used for most applications. ing.

Figure 1 shows the relationship between a single crystal and a crucible when pulling a single crystal using the CZ method. A polycrystal made of the same material as the single crystal is placed, and the crucible 1 is heated by passing an electric current through the carbon heater 2 in an inert atmosphere such as argon (Ar), or by heating the crucible 1 by a method such as high frequency heating. The crystal material is melted to form a melt 3.

Next, the single crystal is grown by dipping the tip of the seed crystal 4 having the crystal orientation desired for crystal growth into the melt 3, but at this time the temperature of the melt 3 is such that the tip of the seed crystal 4 is slightly The temperature is set so that it melts and maintains its balance.
After equilibrium is reached, the crystal is narrowed at a relatively high pulling speed to drive out dislocations in the seed crystal to the outer periphery, suppress the generation of dislocations, and eliminate dislocations.

In order to make the melt 3 uniform and to reduce the temperature difference, the pulling shaft holding the seed crystal 4 and the crucible 1 are rotated at low speed in opposite directions. Now, after the pulled crystal has been made dislocation-free, it is thickened to a desired diameter by lowering the temperature of the melt, and the single crystal is grown in the length direction by being pulled at a constant speed. Necessary conditions for the single crystal grown here include defects such as dislocations, resistivity fluctuations in the radial and pulling directions, and small distribution of oxygen impurities. It is also necessary that there be little fluctuation and that abnormal crystal growth does not occur.

(c) Prior Art and Problems Although the present invention can be applied to the growth of various single crystals, the case of Si, which is a typical semiconductor, will be explained here.

Si is a semiconductor with a melting point of 1410 [°C], and the second
Single crystals are pulled using a pulling device as shown in the figure. Si single crystals usually have a diameter of 4 inches, and crystals with a diameter of 5 inches are now also produced.

In the case of growth with a diameter of 4 inches, after filling the quartz crucible 1 with approximately 20 kg of high-grade Si polycrystalline powder,
By supplying Ar gas from the intake port 5 through a needle valve or gas flow meter and exhausting the air from the exhaust port 6 using a vacuum pump, the degree of vacuum in the device is maintained at approximately 20 [Tor].
r] and energizing the carbon heater 2 to melt the polycrystalline Si.

Next, the seed crystal 4 fixed to the holding frame 7 is immersed in the melt 3 and then pulled up while rotating the molybdenum (Mo) wire 9 holding the holding rod 7 by the motor 8, thereby causing crystal growth. It is being done.

Note that the crucible 1 is also configured to be rotated together with the support base by the motor 10.

When pulling a Si single crystal with a predetermined diameter using such a device, the temperature of the melt 3 must be kept at equilibrium, where the tip of the seed 4 is slightly melted but balanced. This is done by gradually lowering the seed crystal while maintaining the same diameter until it thickens to the desired diameter, and then pulling up the seed crystal.

Here, diameter control in single crystal growth can be performed at both ends of the temperature of the melt 3 and the pulling speed, but the temperature control of the melt 3 is only possible when the weight of the melt 3 is approximately 20 [kg] in this case. It is large and therefore has a large heat capacity and poor response. Therefore, in most cases, the diameter is controlled by adjusting the pulling speed.

However, if the pulling speed is changed significantly, concentration unevenness of toubant impurities, oxygen, carbon, and other impurities appears in the longitudinal direction of the crystal, which is undesirable because it impairs the uniformity of properties. Now, the diameter control as described above is carried out by measuring the temperature with a radiation pyrometer 12 through the viewing window 11 provided at the top of the device and by visual inspection, but it is not possible to obtain a straight-shaped single crystal with a target diameter. required considerable technical skill.

(d) Purpose of the Invention The object of the present invention is to provide a growth method for obtaining a cylindrical single crystal having a uniform diameter while maintaining a constant pulling rate.

(e) Structure of the Invention The object of the present invention is achieved by using a method of pulling a single crystal while irradiating the meniscus line where the pulled crystal and the melt contact with a laser beam.

(f) Embodiment of the Invention An embodiment of the invention will be described below. FIG. 3 is a schematic cross-sectional view of the device used in this example.

In the figure, 21 is a crucible, 22 is a carbon heater, 2
3 is a melt for crystal growth, 24 is a seed crystal, 25 is an intake hole, 2
6 is an exhaust port, 27 is a holding rod, 28 is a motor that rotates the seed crystal 24, 2p is a Mo wire, 30 is a motor that rotates the crucible 21, 31 is a viewing window, 32 is a radiation thermometer, 33 is a meniscus line, Reference numeral 34 indicates a laser source, and 35 indicates a laser beam.

The present invention is a quartz viewing window 3 provided in a pulling device.
1 is used to grow while irradiating the meniscus line 33 with the laser beam 35 emitted from the laser beam generation source 34 to suppress abnormal growth and melt the excess single crystal that has grown laterally. It is something that makes you

That is, a carbon dioxide laser or a YAG laser is used to shine a spot of laser light 35 through a viewing window 31 made of transparent quartz onto the meniscus line 33 where the crystal is being pulled.

Therefore, the present invention works to dissolve abnormal crystals that tend to grow laterally from the meniscus line 33 where the crystals and the melt 23 are in contact with each other by laser irradiation, and immediately eliminate the source of the abnormal crystals even if they occur. In addition, it works to prevent the diameter of the single crystal being pulled from becoming larger than the target value.

To achieve this, it is sufficient to make the crystal thicker by setting the crystal pulling speed somewhat lower than the standard value, and to maintain a state in which a very small portion of the crystal is always melted by laser irradiation. That is, the crystals being grown, including the seed crystal 24, are rotated at about 10 revolutions per minute by the motor 28 on the top of the apparatus, but the sporatra meniscus line 33 of the laser beam 35
The crystal growth type may be performed at a constant pulling rate according to the

(g) Effects of the Invention By carrying out the present invention, abnormal crystal growth can be eliminated, and a cylindrical single crystal having a target diameter can be obtained.

[Brief explanation of the drawing]

Figure 1 is a cross-sectional view showing the relationship between the crucible and melt for pulling a single crystal, Figure 2 is a block diagram of a crystal growth apparatus used in a conventional crystal growth method, and Figure 3 is a diagram showing the structure of a crystal growth apparatus used in this example. It is a block diagram of a growth apparatus. In the figure, 1 and 21 are crucibles, 2 and 22 are carbon heaters, 3 and 23 are melts, 4 and 24 are seed crystals, and 8, 10, 2
8, 30 are motors, 11, 31 are observation windows, 12, 32 are radiation pyrometers, 13, 33 are meniscus lines, 14, 3
5 is a laser beam, and 34 is a laser beam generation source. Kaya/fJ () Figure 2, Figure P3

Claims (1)

[Claims] When pulling a single crystal from a crystal growth melt in a crucible using a seed crystal using the Czyochralski method, the pulling is performed while irradiating the meniscus line where the pulled crystal and the melt contact with the laser. A single crystal growth method characterized by: