The method of growing silicon single crystals

 

(57) Abstract:

The purpose of the invention is the control of oxygen concentration (obtaining a given value of Nabout) dislocation single crystal silicon grown by the Czochralski method. This objective is achieved in that in the method of growing silicon single crystals by Choralschola using installed inside the heater quartz crucible with a diameter of 300 30 mm with respect to the surface area of contact of the melt with the crucible to the area of surface contact of the melt of 1.5 - 4.0 distance (h) from the initial level of the melt in the crucible to the top of the heater support equal to 2 to 9 cm, and the increase (decrease) in the concentration of oxygen in the upper part of growing a single crystal on each of 0.4 0,21017cm-3spend by increasing (decreasing) the level of the melt 1 cm within the interval h. The proposed solution allows to grow silicon single crystals for a broad class of semiconductor devices with different requirements to the oxygen concentration. 1 Il., table 1.

The invention relates to the technology of semiconductor materials, in particular to the technology of growing silicon by the Czochralski method. Monocrystal and power semiconductor technology.

Czochralski method includes the single crystal growth on a monocrystalline seed crystal from a melt of silicon, placed in a quartz crucible. As a result of the interaction of the melt with the walls of the quartz crucible of the growing crystal is enriched with oxygen. The level of oxygen concentration in the Si crystals depending on the type of semiconductor devices and specific technologies of their production should be quite different. So, in the manufacture of integrated circuits (especially VLSI) oxygen concentration (Nabout) must be high enough to effect internal gettering. In silicon, suitable for the production of powerful transistors and devices power semiconductor technology, Naboutthe contrary should be the minimum possible to ensure high thermal stability electrophysical and structural properties of silicon. In connection with the foregoing, a need arises for the development of technological methods management (obtaining a given value of) the oxygen concentration in the grown silicon single crystals.

A method of obtaining single-crystal Si with low oxygen content [1] according to which in rspl is provided in the crystal lattice of the grown silicon oxygen with the formation of new compounds. In the example in [1] for example, with the addition of a Si melt Germany in the amount of 6% by weight of Noin the crystals is reduced by almost 2 times. The disadvantages proposed in [1] of this method include the possibility of a violation dislocation growth or occurrence of some other structural defects associated with the input impurities, especially for growing single crystals of Si large diameter and of great length.

A method of obtaining single-crystal Si c increased oxygen [2] whereby to prevent evaporation of SiO (and therefore, increasing Noin the growing crystal) on the outside surface of the melt is rotating quartz ring with an inner diameter greater than 1.2 times the diameter of the growing crystal.

The disadvantages described in [2] method is the difficulty of ensuring dislocation of crystal growth due to the proximity of the foreign body, as well as some of the problems associated with obtaining good shape as-grown crystals due to the complexity of automatic maintenance of the diameter.

A common shortcoming described in [1] and [2] methods is the fact one-sided impact on the oxygen concentration, i.e. it ASS="ptx2">

A known method of controlling the oxygen concentration in the grown by the Czochralski single crystals of Si by changing factors that affect the hydrodynamics of the flow in the melt Si frequency of rotation of the crystal (Wkr) and the crucible (Wtand Wkr/Wt[3] Thus, in accordance with [3] the oxygen concentration in the upper part of the Si single crystals with a diameter of 75 to 80 mm, grown under conditions of Wkr20 rpm and Wt2 rpm, was more than 1.5 times higher than in the conditions of Wkr0,5 rpm and Wt15 rpm, however, described in [3] the method merely States the fact of the influence of Wt, Wkrand Wkr/Wtbut does not give the necessary guidance oxygen concentration in the desired range of values of Nabout.

The closest solution adopted for the prototype, a method described in [4] was Proposed in [4] the method allows to control the oxygen concentration in the upper parts (in place out on the constant diameter) of single crystals of Si in a fairly wide range by selecting the corresponding relationship of the surface area of contact of the melt with the crucible (Sto) to the area of the open surface of the melt (Sandin the range of 1.5 to 4.0 and the subsequent formulation of owenia melt. So, to obtain the Naboutin the upper part of the Si single crystals with a diameter of 80 mm at the level of 1,21018cm-3( 9,01017cm-3when the calibration coefficient 2,451017cm-2) you must implement the relation Sto/Sand2,8 by using, for example, the crucible with a diameter of 270 mm and loaded into the crucible 16 kg (the recommended value of Wkrand Wtto ensure the specified value of Naboutin [4] are not given).

However, in [4] examined the influence of factors determining the wall temperature of the quartz crucible, namely the design of the shielding thermal unit and the position of the melt within a hot zone setup cultivation. However, it is known that the temperature of the crucible wall leads to a significant change in the dissolution rate of the quartz crucible into the melt of Si, and therefore, to change the number of admissions in the melt (and crystal) oxygen, even when the equal treatment Sto/Sand.

The purpose of the invention, the control of oxygen concentration (obtaining a given value of Nabout) dislocation Si single crystals grown by the Czochralski method.

This objective is achieved in that in the method virusiv is Igla diameter 300 30 mm with respect to the surface area of contact of the melt with the crucible to the area of the open surface of the melt of 1.5-4.0 distance (h) from the initial level of the melt in the crucible to the top of the heater support equal to 2 9 cm, and increase (decrease) in the concentration of oxygen in the upper part of growing a single crystal on every 0,4 0,21017cm-3spend by increasing (decreasing) the level of the melt 1 cm within the specified interval h.

Selects the specified interval of values of h because h is less than 2 cm and more than 9 cm is extremely difficult dislocation growth of the crystal. In addition, when h > 9 cm due to low radial temperature gradient in the melt difficulties with ensuring good shape of the growing crystal. To overcome this limitation would require the application of extremely low speeds cultivation that is not economically feasible.

On the other hand, when grown under conditions of h < 2 cm increases the likelihood of spontaneous crystallization of the melt at the walls of the quartz crucible (the so-called "Pomorski").

The change in oxygen concentration in the crystal when changing the initial position of the melt 1 cm is in the range (0,2-0,6)1017cm-3and is determined by the type of installation: growing by design its thermal unit), as well as the size, shape and material of the elements under the crucible and heat shielding node. Thus, in particular, the experience is) leads to an increase in No/h more than 1.5 times. In the fluctuation value of No/h 0,21017cm-3/cm also includes the error of the method of measuring the concentration of oxygen.

The drawing shows the basic elements of thermal unit of the cultivation, as well as claimed in the invention the parameter h. In the drawing, the following notation: 1 graphite heater; 2 quartz crucible; 3 - Si melt; 4 cylindrical graphite element under the crucible.

Example. The Si single crystals with a diameter of 80, 105 and 155 mm brand KDB 12 crystallographic orientation of <100> were grown in the "Subject-30" in the flow of argon from the crucible with a diameter of 330 mm Cylindrical element under the crucible (item 4 in the drawing) was made in the form of graphite grid. The gas flow was: when growing a single crystal with a diameter of 80 mm 800 l/h, with a diameter of 105 mm 1200 l/h and a diameter of 155 mm 1500 l/h the Rate of cultivation has changed from 1.5 to 0.5 mm/min according to the program. Rotation frequency of the crystal and the crucible was maintained constant, respectively, 20 and 3.minutes

The growing crystal was carried out at different initial position of the melt level in the crucible relative to the heater, for which the crucible was moved by the specified distance.

The concentration to which the communication on the wavelength of 9.1 μm when using the calibration coefficient 2,451017cm-2.

The table lists some additional data on the mode of growing single crystals: mass loading in the crucible, the ratio of Sto/Sandthe value of h, and the results of measurement of Naboutin crystals and value of No/h.

As can be seen from the presented data, in a tested embodiment, thermal design of the site and relationship Sto/Sandby changing the initial position of the melt relative to the heater, it is possible to control the oxygen concentration in the upper parts of the Si single crystals in a fairly wide range: (5-8,5)1017cm-3for crystals with a diameter of 80 mm (5,7 - 9,3)1017cm-3for crystals with a diameter of 105 mm and (7-11)1017cm-3for crystals with a diameter of 155 mm

Thus, the proposed solution allows to grow single crystals of Si for a broad class of semiconductor devices with different requirements for values of Nabout. Thus, the Si single crystals with a diameter of 80 mm with Nabout51017cm-3, grown in accordance with example 3 of the table can be used in the production of power transistors, where the necessary condition is extremely high thermal stability of the electrical resistivity Si.

Data presented in table are also convincing demonstration of the main disadvantage of the method of growing the prototype [4] the crystal growing at the same value of Sto/Sandbut at different position of the melt inside the heat unit of the cultivation, leads to significantly different values of Naboutin crystals. So, for example, single crystals with a diameter of 80 mm, grown in the conditions of implementation of the same relationship Sto/Sand(1,8), but when changing h in the range of 2 to 9 cm, size of Naboutchange within (5-8,5)1017cm-3.

Thus, specified in the application to growing conditions are optimal and expedient from the point of view of achieving the desired positive effect control the oxygen concentration of the dislocation single crystal Si in a wide interval of values. Such crystals can be successfully used in devices of the power semiconductor and electronic equipment.

The method of growing silicon single crystals by Choralschola using fixed inside the area of the open surface of the melt 1,5 4,0, characterized in that the distance h from the initial melt level in the crucible to the top of the heater support equal to 2 to 9 cm, and the increase (decrease) in the concentration of oxygen in the upper part of a growing crystal for every (0,4 0,2) 1017cm-3spend by increasing (decreasing) the level of the melt 1 cm within the specified interval h.

 

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