Method of production of the single-crystal silicon (versions)

FIELD: chemical industry; methods of production of the semiconductive materials.

SUBSTANCE: the invention is pertaining to chemical industry, in particular, to the method of production of the single-crystal silicon and may be used at growing the single-crystal silicon by Czochralski method. The method provides for smelting-down of the source silicon in the crucible, injection of the crystalline seed, the crystal drawing out from the melt in the rotating crucible onto the rotating seed at the coincidence of the direction of rotations of the crucible and the crystal. At that in compliance with the growth of the crystal in process of its production the speed of rotation of the crucible and the speed of rotation of the crystal is a step-by-step increasing at keeping approximately constant the ratio of the speeds of rotation of the crucible and the crystal. The method ensures production of silicon monocrystals with the homogeneous radial distribution of the dopant impurity and oxygen and with the uniform distribution of the required amount of oxygen along the length of the crystal.

EFFECT: the invention ensures production of silicon monocrystals with the homogeneous radial distribution of the dopant impurity and oxygen and with the uniform distribution of the required amount of oxygen along the length of the crystal.

6 cl, 2 ex, 2 dwg

 

The invention relates to the technology of semiconductor materials and can be used for growing silicon single crystals by the Czochralski method, having a homogeneous distribution of oxygen along the length of the crystal.

As you know, when growing a single crystal from a melt by the Czochralski the degree of oxygen saturation of the single crystal along its length associated with the number of silicon monoxide (SiO), which is formed due to reaction between the quartz crucible and the molten silicon (SiO2+Si=2SiO). Moreover, as the growing crystal and, consequently, reduce the volume of the melt surface area of contact between the quartz crucible and the melt is continuously decreasing. These changes of parameters and therefore change the amount allocated to the SiO should be considered when regulating the distribution of oxygen along its length.

Known methods for growing monocrystalline silicon, are tasked with obtaining a uniform distribution of oxygen along the length of the crystal (see, for example, European application 0055619 RF patent No. 2077615 from 13.06.95 year).

In Russian patent surface of the crucible containing the melt consists of a cylindrical and spherical parts, and a homogeneous distribution of oxygen is obtained by changing (increasing or decreasing) the speed of rotation the crucible and maintain a constant speed of rotation of the crystal, moreover, the change of rotation speed of the crucible is carried out depending on which station is the level of the melt, cylindrical or spherical.

The known method, though, and achieves better distribution of oxygen along the length of the crystal, however, is quite complex, since the algorithm changes the rotation speed of the crucible varies significantly for different configurations of the crucible and must account for every inch of length of the crystal.

In the specified European application better distribution of oxygen along the length of the crystal is obtained by increasing the rotational speed of the crucible compared with the speed of rotation of the crystal.

However, in the known methods the rotation of the crucible and the crystal is carried out in opposite directions and by increasing the speed of rotation of the crucible this leads to an inhomogeneous distribution of oxygen and impurities in the cross section of the crystal.

A method of obtaining single-crystal silicon with a homogeneous distribution of oxygen and dopant on the diameter of the crystal, comprising the extrusion of the molten silicon held in crucible, by rotating a seed crystal in which the direction of rotation of the crucible and crystal are the same (mode izobrasheniia), and the ratio of the speeds of rotation of the crucible and crystal are calculated according to a formula that takes into account, in particular, the size of tip and grown crystal (see RF patent №2193079 from 14.04.99). In the known patent solved the problem of obtaining dislocation single crystal silicon with a homogeneous distribution of oxygen and dopant on the diameter of the crystal. Achieving effective solution of this problem, the authors in the known method has not carried out any special actions that control the distribution of oxygen along the length of the crystal.

Therefore, its distribution along the length was not uniform and depended on the ratio of the size of the crucible and the crystal mass loading and other, more detail will be discussed below. This deficiency leads to a negative properties of the whole crystal, worsening complicating its use.

It should be noted that the distribution of oxygen along the length of the crystal in the way of its receipt by the Czochralski depends on many conditions for this process. As the growing crystal volume, and, consequently, the surface area of contact of the melt with a quartz crucible decreases, which leads as the growing crystal to the decrease in the allocation of SiO and to reduce the oxygen content in the crystal. Therefore, in the known methods seek to implement the increase in the rotation speed of the crucible to increase the metabolic process. However, the amount received in the crystal oxygen time depends on the ratio between the diameter of the crucible D tand the diameter of the crystal dtothat determines the size of the free surface of the melt (surface evaporation of silicon monoxide). It is noticed that in the mode izobrasheniia with respect to the Dt/dto>2.7 enrollment in the crystal oxygen decreases significantly during the entire process, if the rotation speed of the crucible and crystal remain unchanged (see figure 1, curve 1). When the ratio of Dt/dto>2,7 until about the middle of the process, which corresponds to the share zakristallizuetsya material g/G=0.4 to 0.6, where G is the mass of the load, g is the mass of the grown ingot, there is a drop in the oxygen content, and after about the middle of the process it increases and reaches to about the oxygen content at the initial stage of the process (see figure 2, curve 1).

It should be noted that depending on the technology of the devices to the desired oxygen content in the crystal can be different. In most cases, there are three oxygen levels: 10-13 ppma, 13-15 ppma and 15-17 ppma.

Known methods for producing monocrystalline silicon does not take into account these circumstances.

Therefore, at the present time, given the strict requirements of the industry there is an urgent need for an improved method of obtaining single-crystal silicon, to whom that would be an even distribution of oxygen and dopants on the diameter of the crystal and uniform distribution of the desired oxygen content along the length of the crystal.

The present invention is to provide a method of obtaining dislocation single crystal silicon, the crystal of which would have a uniform distribution of the required amount of oxygen in length and uniform radial distribution of dopant and oxygen.

The first aspect of the present invention provides a method of obtaining single-crystal silicon, comprising melting a source of silicon in the crucible, the introduction of a crystal seed, pulling the crystal from the melt in a rotating crucible rotating a seed crystal at the coincidence of the direction of rotation of the crucible and crystal, while as the growing crystal during the process of obtaining the rotation speed of the crucible and the rotation speed of the crystal is gradually increased, while maintaining approximately constant the ratio of the speeds of rotation of the crucible and crystal.

The degree of this approximation can be ±0,2 from the calculated value of.

Preferably, the crucible is a body of rotation, and the ratio of the diameter of the crucible to the diameter of the crystals is >2.7, the ratio of speeds of rotation of the crucible and crystal are calculated according to the formula:

where ωTand ωToaccordingly, the rotation speed of the crucible and the crystal, R/mi is;

It is a number in the range from 0.1 to 0.5,

DNRand dMR.accordingly, the inner diameter of the crucible and the nominal diameter of the grown crystal, mm;

hPthe initial depth of the melt in the crucible, mm;

HN- the length of the heating part of the heater, mm;

γ - coefficient positioning, equal to from 0.5 to 3.0, depending on the position of the crucible with the melt in the cavity of the heater and thermal design of the site and a previously determined by experiment.

According to the second aspect of the present invention claimed is a method of obtaining single-crystal silicon, comprising melting a source of silicon in the crucible, the introduction of a crystal seed, pulling the crystal from the melt in a rotating crucible rotating a seed crystal at the coincidence of the direction of rotation of the crucible and crystal, while the process of obtaining a crystal ratio of the rotational speed of the crucible and the speed of rotation of the crystal remain approximately (within ±0,2) constant, approximately until the middle of this process, the rotation speed of the crucible and, accordingly, the speed of rotation of the crystal is gradually increased, and after about the middle of the above process, the rotation speed of the crucible and the crystal, respectively smoothly reduced.

In addition, the ratio of the diameter of tiglat the diameter of the crystal is less than 2.7.

The desired (initial) level of oxygen is ensured by selection of well-known process parameters: flow rate and pressure of the inert gas in the growth chamber, the position of the level of the melt in the cavity of the heater, the loading, the initial rotation speed of the crucible.

The essence of the present invention will be best understood by consideration of the examples of its implementation schedules distribution of oxygen along the length of the crystal (figure 1, figure 2). Figure 1. The distribution of oxygen concentration along the length of the silicon single crystals grown at constant speeds of rotation of the crystal and crucible (curve 1) and with a continuous increase in the speed of rotation of the crystal and crucible from the beginning to the end of the process (curve 2). The diameter of the crucible is equal to 330 mm, the diameter of the crystal - 102,5 mm, loading weight - 22 kg Figure 2. The distribution of oxygen concentration along the length of the silicon single crystals grown at constant speeds of rotation of the crystal and crucible (curve 1) and with a continuous increase in the speed of rotation of the crystal and crucible to g/G=0.5, and then a continuous decrease until the end of the process (curve 2). The diameter of the crucible is equal to 356 mm, the diameter of the crystal - 152.5 mm, loading weight - 40 kg Should be borne in mind that the cylindrical portion of the ingot begins with g/G=0,03-0,05 and ends with g/G=0,95 (5% of the loaded material is usually left in the TIG is (e).

As an example implementation of the present invention can include the following.

Loading source polycrystalline silicon in the amount of 22 kg is placed in a quartz crucible with an outer diameter of 330 mm Vacuum working chamber and control the leaks. Served in the working chamber of the dry purified argon in the number of 1200-1400 nl/hour, and the load is first heated, and then make her melt. The power of the heater is set to the value corresponding to the power by pulling, then stabilize the melt until a temperature 1440-1447°C. the Pressure and the flow rate of argon is set to a value optimal for the process. Raise the rotating speed of 5.5 rpm crucible in its working position, is introduced into the melt, a seed crystal with a diameter of 9.8 mm, rotating at a speed of 12.5 rpm in the same direction as the crucible. After that make pulling the thin neck of the single crystal with a diameter of 2-2,2 mm before the appearance dislocation structure. The speed of extrusion reduce and lower the temperature of the melt before reaching the single crystal of a given diameter equal 102,5±1.5 mm Then the speed of extrusion increases to about 2.0 mm/min and maintain it for 3-5 minutes for a smooth release of the single crystal at a given diameter. The diameter of the crystal control is regulated by the automatic control system. Produce stretching of the cylindrical part of the single crystal with the initial rate of withdrawal ˜1.8 mm/min, which is reduced during the entire process.

During the process of pulling the cylindrical part to maintain the oxygen content along the length of the crystal at the same level as the rotation speed of the crucible and, accordingly, the speed of rotation of the crystal gradually (smoothly) increase, keeping the ratio of these velocities are approximately constant. The ratio of the rotational speed of the crucible and the speed of rotation of the crystal is determined by the formula:

where ωTand ωToaccordingly, the rotation speed of the crucible and crystal rpm;

It is a number in the range from 0.1 to 0.5,

DNRand dMR.accordingly, the inner diameter of the crucible and the nominal diameter of the grown crystal, mm;

hPthe initial depth of the melt in the crucible, mm;

HN- the length of the heating part of the heater, mm;

γ - coefficient positioning, equal to from 0.5 to 3.0, depending on the position of the crucible with the melt in the cavity of the heater and thermal design of the site and a previously determined by experiment.

After cultivation of the cylindrical part of the ingot automatic control system off and made a reverse taper length 65-80 mm

Measurement of the distribution of oxygen along the length of the crystal and the dopant distribution and oxygen on the diameter of the crystal was determined by known methods in accordance with the requirements of the International standard ASTM.

If we consider the graph showing the distribution of oxygen along the length of the crystal (figure 1), with a gradual increase of the rotation speed of the crucible and the crystal line, showing the distribution of oxygen along the length (curve 2), will be close to parallel to the x-axis or at a slight angle to it. This indicates a uniform or close to uniform distribution of oxygen.

In the above example, the implementation was performed for the relationship of the diameter of the crucible to the diameter of the crystal >2,7.

Tests were also carried out for DT=356 mm and dK=152.5 mm when loading 40 kg (figure 2); DT=270 mm and dK=102,5 mm at a load of 16 kg and other combinations. Similar results were obtained. When the ratio of DT/dK<2,7 until about the middle of the process, which corresponds to g/G=0.5 the speed of rotation of the crystal and the crucible was gradually increased, and after about the middle of the process, these speeds were gradually reduced, for example, to the original values. When the oxygen content along the length of the crystal was maintained approximately constant.

It should be noted that these examples made the I does not limit the claims of the applicant, which can be defined by the attached claims, and many modifications and improvements may be made within the framework of the present invention.

1. The method of obtaining single-crystal silicon, comprising melting a source of silicon in the crucible, the introduction of a crystal seed, pulling the crystal from the melt in a rotating crucible rotating a seed crystal at the coincidence of the direction of rotation of the crucible and crystal, while as the growing crystal during the process of obtaining the rotation speed of the crucible and the rotation speed of the crystal is gradually increased, while maintaining approximately constant the ratio of the speeds of rotation of the crucible and crystal.

2. The method according to claim 1, where the crucible is a body of rotation, and the ratio of the diameter of the crucible to the diameter of the crystal is >2,7.

3. The method according to claim 1, where the ratio of the speeds of rotation of the crucible and crystal are calculated according to the formula

where ωTand ωToaccordingly, the rotation speed of the crucible and crystal rpm;

It is a number in the range from 0.1 to 0.5;

DNRand dMR.accordingly, the inner diameter of the crucible and the nominal diameter of the grown crystal, mm;

hPthe initial depth of the melt in the crucible, mm;

HN- d is in the heating part of the heater, mm;

γ - coefficient positioning, equal to from 0.5 to 3.0, depending on the position of the crucible with the melt in the cavity of the heater and thermal design of the site and predetermined by experiment.

4. The method of obtaining single-crystal silicon, comprising melting a source of silicon in the crucible, the introduction of a crystal seed, pulling the crystal from the melt in a rotating crucible rotating a seed crystal at the coincidence of the direction of rotation of the crucible and crystal, while the process of obtaining a crystal ratio of the rotational speed of the crucible and the speed of rotation of the crystal remain approximately constant, approximately until the middle of this process, the rotation speed of the crucible and, accordingly, the speed of rotation of the crystal is gradually increased, and after about the middle of the above process, the rotation speed of the crucible and the crystal and consequently reduced.

5. The method according to claim 4, where the crucible is a body of rotation, and the ratio of the diameter of the crucible to the diameter of the crystal is <2,7.

6. The method according to claim 4, where the ratio of the speeds of rotation of the crucible and crystal are calculated according to the formula

where ωTand ωToaccordingly, the rotation speed of the crucible and crystal rpm;

K - the number and the interval from 0.1 to 0.5;

DNRand dMR.accordingly, the inner diameter of the crucible and the nominal diameter of the grown crystal, mm;

hPthe initial depth of the melt in the crucible, mm;

HN- the length of the heating part of the heater, mm;

γ - coefficient positioning, equal to from 0.5 to 3.0, depending on the position of the crucible with the melt in the cavity of the heater and thermal design of the site and predetermined by experiment.



 

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1 dwg 1 o

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1 dwg

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2 cl, 4 ex, 1 tbl

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