JPS5874594A - Growing method for crystal - Google Patents

Abstract

PURPOSE:To control the concn. of the components constituting a vessel for containing of liquid for growing a crystal having electric conductivity contained in said crystal accurately over a wide range by changing the number of revolutions of said vessel in the stage of pulling up the crystal in a magnetic field. CONSTITUTION:A cooling jacket 6 is disposed on the outer side of a heating means 4 disposed in a cylindrical surface shape along the outside circumferential surface of a vessel 2, and, for example, a generating means for DC magnetic fields consisting of a permanent magnet or an electromagnet is disposed on the outer side thereof. While, for example, an Si single crystal seed 8 is rotated, said seed is pulled up in the magnetic field by the means 7 to grow an Si single crystal 10 from an Si melt 3. In this case, a vessel 2 contg. the melt 3 having electric conductivity of a certain degree, for example, a quartz crucible is rotated and the rotating speed thereof is controlled, whereby the concn. of the oxygen in the constituting components of the vessel 2 in the pulled up crystal 10 is changed.

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. I'll do it so I can do it? So, there it is.

The Czochralski method (hereinafter referred to as CZ method) is a method for obtaining a single crystal, for example a silicon single crystal. Sara K
In the 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&! If the crystal growth liquid has electrical conductivity, applying a magnetic field to it increases its effective viscosity, which is thought to suppress thermal convection and liquid surface vibration of the crystal growth liquid. It will be done. That is, when a fluid having electrical conductivity, that is, a conductor, moves in a magnetic field, a potential difference is generated in the fluid, and a current flows. The fluid carrying this current then experiences 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 the adhesiveness appears to be improved.

The stiffness is called magnetorheological. It is thought that due to the magnetic viscosity generated in this way, convection occurs in the fluid, that is, the crystal growth liquid, and C<. It should be noted that if this single crystal is grown in a magnetic field, for example, the Journal of Applied Fixtures
of Applied Physics) Vol.
, 37, No. 5, P., 2021 (196
6), and Journal of Materials Science x
yx (Journal of Materials
8ctence) 5 (1970) P, 822, etc.

The present invention is based on the ability to accurately control the concentration of impurities, such as oxygen concentration, in the grown crystal over a wide range as described above in a crystal growth method in which the crystal is pulled in a magnetic field. It is something to do. In other words, when using the C2 method, it has been recognized that oxygen, which is a component of the container in which the crystal growth liquid is stored, such as a quartz container, is mixed into the grown crystal. Even when using the CZ method, in which crystal growth is performed without a magnetic field, the number of rotations of the crystal to be pulled, the number of rotations of the crucible, the relative direction of rotation, and the temperature of the crucible can be controlled. However, in the CZ method where such a magnetic field is not applied, the viscosity of the crystal growth liquid is low and convection is likely to occur in it, as described above. Therefore, there is a large friction between the liquid and the quartz crystal due to the relative movement WJJFc, and this causes a large amount of oxygen to be taken into the liquid, resulting in a high oxygen concentration in the grown crystal. range in,
i.e. approximately 1~2x1;01tOR'II/Cm
This is a narrow range.

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 formed outside the active region of a semiconductor device and heat treatment is performed, harmful impurities such as Fe, Ou, 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 a semiconductor device. In addition, at a high oxygen concentration that does not generate oxygen precipitates, it has the effect of suppressing the generation and increase of dislocations due to oxygen clustering. In other words, it suppresses the generation and increase of dislocations during heat treatment during the manufacture of semiconductor devices. obtain. 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. Thus, it is possible to obtain a crystal with high resistivity, which was conventionally obtained by the floating gene method (FZ method), and it also becomes possible to manufacture high-voltage, high-output semiconductor devices.

Product quality < It is difficult to increase the diameter of crystals produced by the FZ method, and C
When using the Z method, it is relatively easy to increase the diameter, so controlling the oxygen concentration using the CZ method is advantageous in producing various semiconductor devices at low cost.

In the present invention, in order to obtain such various effects, a crystal which can select oxygen concentration over a wide range,
For example, a crystal growth apparatus capable of obtaining silicon single crystals is provided.

The present invention will be explained in detail below. A crystal growth apparatus 1 for carrying out the method of the present invention will be described with reference to FIG. 1. In the figure, (1) indicates the apparatus as a whole.

+2) is a container, such as a quartz crucible, containing a liquid such as a Si melt (3) for crystal growth having a certain degree of electrical conductivity, and this container +21 is rotated about its central axis. The number of revolutions is selected. A heating means (4) is arranged around the outer periphery of this container 21.

In this heating means (4), an energized heater (5) is arranged, for example, in a cylindrical shape along the outer circumferential surface of the zigzag pattern container (21). Accordingly, for example, a cylindrical heat shield or a jacket (6) cooled by water cooling, etc., is arranged, and a DC magnetic field generating means (7) made of a permanent magnet or an electromagnet, for example, is arranged outside the jacket (6). (8) is a single crystal seed, for example 81 single crystal seed, and (9) is its pulled chicken). The single crystal seed is pulled up by this pulling chuck while rotating along the central axis of rotation of the container 21.

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 1 kHz or more. It has been confirmed that when such a current is applied, unnecessary movements caused by the action of the heating means (4) with m* can be avoided.

In this way, the Si crystal (II) is grown by pulling the SI seed (8) from the Sl melt surface at a required speed. In this case, as described above, the seed 18),
L, therefore, the single crystal that is pulled and grown from this (pulling and growing is performed while rotating II, but I
f! IK In the present invention, the rotational speed of the container f2j is controlled to pull it up.

That is, in the present invention, by rotating the container (2) in this way and controlling its rotation speed, the concentration of oxygen, which is a component of the container (21), in the crystal αO pulled is changed. This is a crystal growth method based on the polishing of the grains.・In this way, when pulling a crystal in a magnetic field, the concentration of, for example, oxygen in the crystal ae changes due to the rotation of the container (21). The container (
As a result of the 2) transition, the container (2) and the crystal growth liquid (3) housed therein whose effective viscosity has been increased by the applied magnetic pressure are rotated relative to each other. liquid (3)
and the inner wall surface of the container +2), and as a result, oxygen from the constituent components of the container +21, such as quartz, dissolves into the liquid (3) and the rubbing becomes large. In other words, as the relative rotational speed of the container (2) to the liquid (3) K increases, the amount of infiltration into the liquid (3) increases, and the oxygen concentration in the crystal aI pulled from this increases. . It was also confirmed that the oxygen concentration in this crystal can be made higher than that in the case where no magnetic field is applied by increasing the rotation speed of the container sufficiently in state 11 when an electromagnetic field is applied.

It is desirable that the single crystal cll to be pulled be rotated from the perspective of the thermal center of the high temperature part and thermal symmetry, but the forced convection caused by the rotation of the crystal will cause the liquid (3) to flow inside the container (2). If there is any contact with the wall, this is oxygen #
However, forced convection such as
If the distance between the crystal and the inner wall of the container (2) is selected so that the crystal does not reach the inner wall of the container (21), the oxygen concentration can be controlled by the rotation of the container (21).

Figure 2 shows the distance between this crystal and the vessel (210 inner firefly surface).
When cod was selected and the crystal rotation speed was set to 3 Or pm, and the rotation speed of a container made of a quartz crucible was rotated at 0.1 rpm in the opposite direction, the liquid (3
) That is, it shows the results of measuring the degree of oxygen in the grown crystal ae when the strength of the magnetic field applied to the 8M 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 of the container (2) as long as the rotation speed is constant.

Further, FIG. 3 shows the measurement of the oxygen concentration in the crystal ao when the rotation speed of the crystal α was changed, and in this case, the rotation speed of the rotor 121 was set to 0.1 rpm.

Curves Qυ and Qz in Fig. 3 represent the case where no magnetic field is applied and the case where a magnetic field of 3500 Gauss is applied when the distance between the crystal 00 and the inner wall surface of the container (2) is set to 56111:is, respectively. 46111 constant curve of
The curve ff1j123 is a case where the distance between the crystal and the inner wall surface of the container +21 is selected to be 691 when a magnetic field of 3500 caus is applied. As is clear by comparing the curve Qυ with the curves @ and (c), when the rotation speed of the container 121 is constant,
It can be seen that when a magnetic field is applied, the oxygen concentration is lower and the dependence on the crystal rotation speed is smaller than when no magnetic field is applied. In addition, as is clear from comparing the curves, the larger the distance between the crystal a1 and the inner wall of the container (21), the smaller the influence of the change in the crystal rotation speed on the oxygen a degree in the crystal. I know what will happen.

In addition, Figure @4 shows that the oxygen concentration distribution in the crystal becomes more uniform as the rotation speed of the container (2:) is determined to be 0.1 rpm and the rotation speed of the crystal changes.

　　　　　　　.

Figure 5 shows the pulling of the crystal under the condition that the rotational speed of the pulled crystal is 5 Orpm and the rotational speed of the container (2) is 2Orpm, and the magnetic field applied to each part A, B, and C is 3500 Gauss and 0 Gauss, respectively. , 3500 Gauss, and the oxygen concentration in each part A and B%CK is shown.As is clear from this, the difference between 1[ and It can be seen that different parts can be formed.

Furthermore, %Figure 6 shows the measurement of 11 degrees of oxygen in the crystal (!) when the rotation speed of the container +23 was changed;
The mark is when the rotation speed of 1 it of crystal is 5 Orpm,
The Δ mark indicates each measured value at 30 rpm. In this case, the strength of the magnetic field was set to 3500 Gauss, but as is clear from Fig. It can be seen that a higher degree of S can be obtained than by indulging in the cz method in which no By selecting the rotation speed of this container 12+, the oxygen concentration in the crystal is 2.5
O” atoms/cm3, the crystal a
It can be seen that the oxygen concentration in e can be changed by about an order of magnitude. :.

As is clear from the above, by rotating the container 121, the oxygen concentration in the crystal αω can be changed from a low a degree to a high a degree, and in this case, as shown in FIG. It is not clear from what I explained in 5 & C. If the applied magnetic field is set at 1500 gauss or higher, it is possible to avoid the influence of magnetic field fluctuations on the oxygen a degree, and as explained in Fig. 3, the crystal u1 When selecting a sufficiently large distance between the inner wall surface of the container 121 and the inner wall surface of the container 121, for example, 69 degrees, it is possible to avoid the influence of the rotation speed of the crystal αG on the oxygen degree in the crystal QIJ. Crystal αω only by controlling the number
For example, since the concentration of oxygen in the reactor can be controlled, this concentration can be set accurately. And, the selection range of this -mutter is I
It has a wide range of s/am3. As mentioned above, by selecting a large distance between the busy crystal Ql and the inner wall surface of the container 12), the rotation speed of the crystal (II) can be arbitrarily selected. As shown, the rotation speed can be selected to be about 3 Orpm or more, which is the speed at which a uniform a-degree distribution can be obtained in the radial direction in the crystal. ・'1 As described above, according to the present invention, Oxygen concentration in crystal tl
The radial direction, that is, the cross-sectional area of l, can be made uniform in each part, and the concentration can be controlled over a wide range, so as mentioned at the beginning, it is possible to suppress The concentration must be selected to obtain the thermal donor effect, or the concentration must be selected to obtain the thermal donor effect.
Alternatively, it is possible to select a concentration that does not cause these effects, and the oxygen concentration can be selected according to the purpose, which is of great practical benefit.

Furthermore, when using the method of the present invention, the concentration distribution in the cross section of the crystal (II) is made uniform, and the rotation speed of the container (2) is changed once in the pulling direction depending on the pulling and growing position of the crystal αω. Therefore, it is possible to form layers with different #I#'# degrees, so for example, as shown in Figure 7, with respect to the pulling direction of the crystal α, the oxygen concentration is about 2 X I Q17 atoms/cm3. with a low layer 0υ and its concentration is, for example, 2.5X1018a t
By sequentially forming layers (2) with a height of about 100 ms/cm and cutting out a wafer from this crystal uI, for example, as shown in figure W48, the part that will become the active region of the semiconductor device can be formed with a low concentration layer 6υ. , the back surface thereof is constituted by a high concentration layer c & 211/c, and by heat treatment, defects caused by the high concentration of oxygen present near the layer 0 are formed on the back surface of the active region, and due to this defect existing in the active region. Gettering of harmful impurities and defect-generating nuclei can be performed.

Alternatively, the crystal aG itself may be doped with a p-type impurity when it is pulled, and depending on the pulling position, the number of revolutions of the container (2H) may be changed to create a layer with a high oxygen concentration and a layer with a low oxygen concentration in the direction of pulling the crystal a1. 1- and are repeatedly stacked to form a crystal, and through subsequent heat treatment, a thermal donor is generated and the portion with high oxygen me becomes n-type,
A cooking diode can also be obtained by repeated lamination with p-type layers of low acidity.

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 a semiconductor device with good characteristics can be manufactured at a low cost.
Its industrial benefits are enormous.

[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 for explaining the present invention, and FIG. 7 is a diagram showing measurement curves obtained by the crystal growth apparatus according to the present invention. An example cross-sectional view of the crystal, and FIG. 8 is an enlarged cross-sectional view of a wafer obtained from this. (11 is a crystal growth device, +21 is a storage container for the crystal material liquid (3), (4) is a heating means, (5) is its heater, (
7) is a magnetic field generating means, (8) is a single crystal seed, (1(I)
is a grown crystal.

Claims (1)

[Claims] A container containing a crystal growth liquid having electrical conductivity, a means for pulling the crystal from the liquid, a means for applying a magnetic field to the liquid, and a means for rotating the container are provided, and the number of rotations of the container is adjusted. 1. A crystal growth method characterized by controlling the concentration of container constituents in the crystal by changing.