JPH0244799B2 - KETSUSHOSEICHOHOHO - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for growing crystals of various materials such as semiconductors, dielectrics, and magnetic materials, and in particular allows the concentration of impurities such as oxygen in the crystal to be controlled over a wide range and accurately. It is intended to do so.

The Czyochralski method (hereinafter referred to as the CZ method) is a method for obtaining a single crystal, such as a silicon single crystal. Furthermore, in this CZ method, a method has been proposed in which a magnetic field is applied to the crystal growth liquid used to grow the single crystal to pull the single crystal. In the single crystal grown by this method, the occurrence of swirl-like defects and growth stripes is reduced.
This is because when a crystal growth liquid has electrical conductivity, applying a magnetic field to it increases its effective viscosity, suppressing thermal convection and liquid surface vibration of the crystal growth liquid. It seems to be based on. That is, a fluid that has electrical conductivity in a magnetic field,
In other words, when a conductor moves, a potential difference is generated in this fluid, and a current flows. As a result of the current flowing in this magnetic field, the fluid carrying this current receives a new force. Since this force is in the opposite direction to the direction in which the fluid moves, the movement of the fluid becomes slower and its viscosity increases. This is called magnetic viscosity. It is thought that the generation of magnetic viscosity makes it difficult for convection to occur in the fluid, that is, the crystal growth solution. Regarding growing this single crystal in a magnetic field, for example, the Journal of Applied Physics (Journal of Applied Physics)
Applied Physics）Vo1.37, No.5, P.2021
(1966), and Journal of Materials
Science (Journal of Materials Science) 5
(1970) P.822 etc.

The present invention is a method for growing a crystal in which the crystal is pulled in a magnetic field, in which the concentration of impurities, such as oxygen concentration, in the grown crystal can be controlled over a wide range and accurately as described above. It is. In other words, when using the CZ method,
Although it has been recognized that oxygen, a component of the container in which the crystal growth liquid is stored, such as a quartz container, is mixed into the grown crystal, conventional magnetic fields are not applied. Even in the case of the CZ method, in which crystals are grown in Although control is possible, the CZ method does not provide such a magnetic field.
As mentioned above, since the viscosity of the crystal growth liquid is low and convection is likely to occur in it, there is a large amount of friction between this liquid and the quartz crucible due to relative movement.
Therefore, the oxygen concentration in the crystal grown by increasing the amount of oxygen taken into the liquid is in a high concentration range, that is, in a narrow range of approximately 1 to 2×10 ¹⁸ atoms/cm ³ .

On the other hand, oxygen in a semiconductor single crystal, such as a silicon single crystal, has various effects depending on its concentration and distribution on the characteristics of the semiconductor device obtained therefrom or on the heat treatment during the manufacturing process. For example, when this oxygen concentration is relatively high, stacking faults and oxygen precipitates are generated by heat treatment, which adversely affects the characteristics of the semiconductor device. However, when such defects are created outside the active region of a semiconductor device and heat treatment is performed, harmful impurities such as Fe, Cu, etc.
It performs a so-called intrinsic gettering action to getter metal impurities such as Au, and has the effect of improving the characteristics of semiconductor devices. Furthermore, at an oxygen concentration high enough not to generate oxygen precipitates, it has the effect of suppressing the generation and increase of dislocations due to oxygen clusters. That is, the occurrence and increase of dislocations during heat treatment during manufacturing of semiconductor devices can be suppressed.
Furthermore, when the oxygen concentration in the crystal is high, the oxygen in the silicon generates thermal donors by heat treatment at the required temperature, e.g. 450°C, and has the effect of converting it to n-type. However, at low oxygen concentrations, the generation of thermal donors is reduced. The conventional floating zone method (FZ)
It is now possible to obtain crystals with high resistivity, which was obtained by the method (method), and it also becomes possible to manufacture high-voltage, high-output semiconductor devices. Incidentally, it is difficult to increase the diameter of crystals produced by the FZ method, whereas it is relatively easy to increase the diameter of crystals produced by the CZ method.The fact that oxygen concentration can be controlled by the CZ method is useful for various semiconductor devices. This is advantageous in terms of obtaining it at a low price.

The present invention provides a crystal growth method that makes it possible to obtain crystals, such as silicon single crystals, in which oxygen concentrations can be selected over a wide range in order to obtain these various effects. .

The present invention will be explained in detail below. A crystal growth apparatus for carrying out the method of the present invention will be described with reference to FIG. 1. In the figure, numeral 1 indicates the apparatus as a whole.
Reference numeral 2 denotes a container, such as a quartz crucible, in which a crystal growth melt or solution liquid having a certain degree of electrical conductivity, such as a Si melt 3, is contained, and this container 2 is configured to rotate about its central axis. , and furthermore, the number of rotations thereof is selected. A heating means 4 is arranged around the outer periphery of this container 2 . The heating means 4 is arranged such that the energized heaters 5 form a cylindrical surface along the outer peripheral surface of the container 2 in, for example, a zigzag pattern. Outside the heating means 4, for example, a cylindrical heat shield or a jacket 6 cooled by water cooling or the like is disposed as required, and on the outside thereof, for example, a DC magnetic field generating means made of a permanent magnet or an electromagnet is arranged. 7 is placed. 8 is a single crystal seed, for example a Si single crystal seed, and 9 is its pulling chuck. The single crystal seed is pulled up by this pulling chuck while rotating along the central axis of rotation of the container 2.

Electricity is supplied to the energizing heater 5 of the heating means 4 using a substantially direct current with ripple content suppressed to 4% or less.
Or an alternating current or pulsating current of 1KHz or more. It has been confirmed that when such a current is applied, unnecessary vibrations caused by the interaction of the heating means 4 with the magnetic field can be avoided.

In this way, the Si crystal 10 is grown by pulling the Si seed 8 from the Si melt surface at a required speed. In this case, as mentioned above, the seed 8 and therefore the single crystal 1 to be grown by pulling
The pulling growth is carried out while rotating the container 2. In particular, in the present invention, the pulling is carried out by controlling the rotational speed of the container 2.

That is, in the present invention, by rotating the container 2 in this way and controlling the rotation speed, the concentration of oxygen, which is a component of the container 2 described above, in the pulled crystal 10 changes. This is a crystal growth method based on the discovery that
In this way, during crystal pulling in a magnetic field, the concentration of, for example, oxygen in the crystal 10 changes due to the rotation of the container 2. and the crystal growth liquid 3 whose effective viscosity has been increased by the application of a magnetic field is rotated relative to each other to cause the required rubbing between the liquid 3 and the inner wall surface of the container 2, As a result, the oxygen in the constituent components of the container 2, such as quartz, dissolves into the liquid 3, and the greater the friction between them, that is, the greater the relative rotational speed of the container 2 with respect to the liquid 3, the more oxygen is dissolved into the liquid 3. As the amount increases, the oxygen concentration in the crystal 10 pulled from this increases. It was also confirmed that the oxygen concentration in this crystal can be made higher than when no magnetic field is applied by sufficiently increasing the number of revolutions of the container when a magnetic field is applied.

Note that it is desirable that the single crystal 10 to be pulled is rotated from the viewpoint of the thermal center of the high temperature part and thermal symmetry, but the forced convection caused by the rotation of the crystal causes the liquid 3 to come into contact with the inner wall surface of the container 2. If this occurs, it will affect the oxygen concentration, but the distance between the crystal and the inner wall of the container 2 is selected so that such forced convection does not reach the inner wall of the container 2. In this way, the oxygen concentration is controlled by rotating the container 2.

Figure 2 shows the distance between this crystal and the inner wall of container 2.
56 mm, the crystal rotation speed is 30 rpm, and the rotation speed of container 2, which is a quartz crucible, is rotated at 0.1 rpm in the opposite direction.
That is, it shows the results of measuring the oxygen concentration in the grown crystal 10 when the strength of the magnetic field applied to the Si melt was varied. As is clear from this, when the applied magnetic field is 1500 Gauss or more, there is almost no change in the oxygen concentration as long as the rotation speed of the container 2 is constant.

Further, FIG. 3 shows the measurement of the oxygen concentration in the crystal 10 when the rotation speed of the crystal 10 was changed, and in this case, the rotation speed of the container 2 was set to 0.1 rpm. And curves 21 and 22 in Figure 3
are the distances between the crystal 10 and the inner wall of the container 2, respectively, 56
Curve 23 shows the distance between the crystal and the inner wall of container 2 of 69 mm when a magnetic field of 3500 Gauss is applied and when no magnetic field is applied and when a magnetic field of 3500 Gauss is applied. This is the case when selected. Curve 21 and curves 22 and 2
As is clear from comparison with 3, when the rotation speed of the container 2 is constant, when a magnetic field is applied, the oxygen concentration decreases compared to when no magnetic field is applied, and the dependence of the crystal rotation speed increases. It can be seen that the gender is small. Furthermore, as is clear from comparing curves 22 and 23, the larger the distance between the crystal 10 and the inner wall surface of the container 2, the less the effect of changes in the crystal rotation speed on the oxygen concentration in the crystal. I understand that.

In addition, Figure 4 shows the rate of change in oxygen concentration in the diametrical direction of the crystal with respect to the change in crystal rotation speed when the rotation speed of container 2 is selected to be 0.1 rpm, that is, maximum concentration - minimum concentration / maximum concentration x 100. It is something. As is clear from this, it can be seen that as the crystal rotation speed increases, the oxygen concentration distribution in the crystal becomes more uniform.

In Figure 5, the rotation speed of the pulled crystal is 50 rpm,
With the rotation speed of the container 2 at 20 rpm, the magnetic field applied to each part A, B, and C of the crystal was 3500 rpm.
The results of measuring the oxygen concentration in each part A, B, and C when changing it to Gauss, 0 Gauss, and 3500 Gauss are shown, and it is clear from this that the concentration of oxygen depends on whether or not a magnetic field is applied to the growing crystal. It can be seen that portions with different concentrations can be formed.

Furthermore, FIG. 6 shows the measurement of the oxygen concentration in the crystal 10 when the rotation speed of the container 2 was changed.
In the figure, the ○ mark indicates each measured value when the rotation speed of the crystal 10 was set to 50 rpm, and the △ mark indicates each measured value when the rotation speed was set to 30 rpm.
In this case, the strength of the magnetic field was 3500 Gauss, but as is clear from Fig. 6, even when a magnetic field is applied, if the rotation speed of the container 2 is increased,
In fact, it can be seen that a higher concentration can be obtained than in the conventional CZ method in which no magnetic field is applied. By selecting the rotation speed of this container 2, the crystal 1
The oxygen concentration in the crystal 10 can be as high as 2.5×10 ¹⁸ atoms/cm ³ , and the oxygen concentration in the crystal 10 can be changed by about one order of magnitude within the range of the rotation speed of the container 2 from 0.1 to 20 rpm. Recognize.

As is clear from the above, by rotating the container 2, the oxygen concentration in the crystal 10 can be changed from a low concentration to a high concentration. As is clear from the above, if the applied magnetic field is selected to be 1500 Gauss or higher, it is possible to avoid the influence of magnetic field fluctuations on the oxygen concentration, and as explained in Figure 3, the crystal 10
Make the distance between the inner wall of container 2 sufficiently large, for example 69
mm, it is possible to avoid the influence of the rotational speed of the crystal 10 on the oxygen concentration in the crystal 10, and therefore the oxygen concentration in the crystal 10 can be controlled only by controlling the rotational speed of the container 2. Settings can be made accurately. The selected concentration range is a wide range of 1×10 ¹⁷ to 2.5×10 ¹⁸ atoms/cm ³ . As mentioned above, by selecting a large distance between the crystal 10 and the inner wall surface of the container 2, the rotation speed of the crystal 10 can be arbitrarily selected. As shown, the rotation speed can be selected to be about 30 rpm or more, which is the speed at which a uniform concentration distribution in the radial direction in the crystal can be obtained.

As described above, according to the present invention, the oxygen concentration can be made uniform in each part in the radial direction, that is, in the cross section of the crystal 10, and the concentration can be controlled over a wide range. As mentioned above, it is possible to select a concentration that produces an intrinsic gettering effect, a concentration that produces a thermal donor effect, or a concentration that does not produce any of these effects, depending on the purpose. Since the oxygen concentration can be selected according to the situation, the practical benefits are extremely large.

Further, when using the method of the present invention, the concentration distribution in the cross section of the crystal 10 is made uniform, and the concentration in the pulling direction is changed by changing the rotation speed of the container 2 depending on the pulling and growing position of the crystal 10. Since layers with different oxygen concentrations can be formed,
For example, as shown in FIG. 7, with respect to the pulling direction of the crystal 10, the oxygen concentration is, for example, 2
For example, by sequentially forming a layer 31 with a low concentration of about 10 ¹⁷ atoms/cm ³ and a layer 32 with a high concentration of about 2.5×10 ¹⁸ atoms/cm ³ and cutting a wafer from this crystal 10, As shown in FIG. 8, the part that will become the active region of the semiconductor device is formed of a low concentration layer 31, the back surface of which is formed of a high concentration layer 32, and heat treatment is performed to increase the high concentration of the layer 32. Defects caused by the concentration of oxygen can be formed on the back surface of the active region, thereby gettering harmful impurities and defect generation nuclei present in the active region.

Alternatively, the crystal 10 itself may be doped with a p-type impurity when the crystal 10 is pulled, and the rotation speed of the container 2 may be changed depending on the pulling position.
A layer with high oxygen concentration and a layer with low oxygen concentration are repeatedly stacked to form a crystal in the pulling direction of zero, and through subsequent heat treatment, a thermal donor is generated and the portion with high oxygen concentration becomes n-type. A stacking diode can also be obtained by repeatedly stacking a p-type layer with a portion having a low oxygen concentration.

As described above, according to the present invention, for example, the oxygen concentration in the crystal can be selected over a wide range, so that semiconductor devices with various good characteristics can be manufactured at low cost, and the industrial benefits thereof are enormous. be.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an example of an apparatus for carrying out the crystal growth method according to the present invention, FIGS. 2 to 6 are measurement curve diagrams used to explain the present invention, and FIG. FIG. 8 is an enlarged cross-sectional view of a wafer obtained from this. Reference numeral 1 designates a crystal growth apparatus, 2 a storage container for a crystal material liquid 3, 4 a heating means, 5 a heater thereof, 7 a magnetic field generating means, 8 a single crystal seed, and 10 a grown crystal.

Claims (1)

[Claims] 1. A container containing an electrically conductive crystal growth liquid, means for rotating and pulling up a crystal from the liquid, means for applying a static magnetic field in a predetermined direction to the liquid, and means for rotating the container. The distance between the crystal and the inner wall surface of the container is such that the concentration of the container constituent components in the crystal does not depend on the rotation speed of the crystal, and the rotation speed of the container is changed to A crystal growth method characterized by controlling the concentration of constituent components of a container.