The method of growing silicon single crystals

 

(57) Abstract:

The invention relates to growing silicon single crystals by the Czochralski method with a uniform distribution of oxygen along the length of the crystal in its dislocation structure, which allows the use of these crystals in the manufacture of integrated circuits with a high level of integration. This is achieved in that in the method of growing silicon single crystals by pulling on a rotating seed crystal from the melt in the crucible, the surface of which is successively from cylindrical and spherical parts, including changing the frequency of rotation of the crucible and maintaining a constant speed crystal (WCR.), when Wkr>Wtthe change of frequency of rotation of the crucible (Wtas cultivation is carried out in a matter in what part of the crucible, the melt level: cylindrical or spherical. When the crystal is grown from the cylindrical part of the crucible Wtincreasing on (0,1-0,5) rpm, and when the cultivation of the spherical part of the crucible is reduced to (0,15-0,45) rpm per inch of length of the crystal. 1 table, 1 Il.

The invention relates to methods of obtaining poluprovodnikov the manufacture of integrated circuits with a high level of integration. This 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. Continuous decrease of the melt in the crucible as the growing crystal using a constant frequency of rotation of the crucible (Wt) and crystal (Wkr) leads to non-uniform distribution of oxygen concentration (No) along the length of the crystal.

The known method of increasing the uniformity of distribution of oxygen along the length of the crystal as it is growing [1] In accordance with [1] Wkrincreases linearly in the range of 0.05 to 0.2 rpm per inch of length of the crystal. However, this method does not provide a uniform distribution of oxygen along the length of the crystal, because it does not take into account the complex nature of change Nodue to increasingly design currently in quartz crucibles.

There is also known a method of increasing the uniformity of distribution of oxygen along the length of the single crystal silicon [2] according to which the melt is lowered quartz tube through Motorauthority problems associated with the introduction of the quartz tube in the working area of installation of cultivation, as well as the high probability of failure dislocation of crystal growth due to the possible ingress of silica fume on the front of crystallization of the melt.

Known methods of increasing the uniformity of distribution of oxygen along the length of the crystal by changing the rotational speed of the crucible as the growing crystal at a constant value of WCR.. Thus, in [3] it is proposed to change the rotational speed of the crucible according to the following law:

grad WtK grad No,

where To positive (or negative) value depending on the temperature gradient between the periphery and center of the melt.

However, this method is very time consuming, because each specific ways of growing it is necessary to measure the oxygen concentration along the length of the crystal at a constant Wtthe measurement of the temperature gradient in the melt.

Closest to the proposed solution method is described in [4] it to improve the uniformity of the distribution) the rotational speed of the crucible continuously increase as the growing crystal. However, the crystal and the crucible are rotated in opposite directions and in% the th uniform distribution) along the entire length of the crystal. Set that as the growing single crystal oxygen concentration may decrease or increase depending on what part of the crucible, the melt (cylindrical or spherical). The application as proposed in [4] method with a constant W^krcontinuously increasing with the growing Wtnot provides No alignment along the entire length of the crystal. Another drawback is proposed in [4] method is the difficulty in implementing recommended to ensure Wkr>Wtfrequency of crystal rotation on installations with flexible upper stem (all given in [4] examples Wkr28 rpm). Upon reaching Wkr28 rpm and greater probability of excitation of the crystal, which can lead to the distortion of its shape and disruption dislocation growth.

The purpose of the invention increase the homogeneity of the distribution of oxygen along the length of the crystal in its dislocation structure.

This objective is achieved in that in the method of growing silicon single crystals by pulling on a rotating seed crystal from the melt in the crucible, the surface of which is sequentially composed of cylindrical and spherical parts, on the of the single crystal under the condition Wkr>Wt, the rotational speed of the crucible for growing a crystal of the cylindrical part of the crucible increase (0,2-0,5) rpm, and when the cultivation of the spherical part of the crucible is reduced to (0,15-0,45) rpm per inch of length of the crystal [1]

Determination of changes in sign and magnitude carried out by the method of pre-calculating the length of the crystal grown from different parts of the crucible. To indicate the points of change of the amount it is possible to use other methods, such as special marks on the surface of the crucible during manual control of the process and so on, the Choice of the above ranges of Wtdue to achieve the most positive effect in the larger and smaller values do not ensure the required degree of homogeneity of the distribution). In addition, with increasing Wtmore than 0.5 rpm per inch of length of the crystal due to the high Wkrnecessary to implement the terms Wkr>Wtpossibly the appearance of swinging crystal, distortion of its shape, which leads to the violation of dislocation growth.

Example.

The silicon single crystal with a diameter of 155 mm, grade KDB 7,5, [100] was grown in the "Subject-30" in the flow of argon is and 1500 l/h at a residual pressure of 9.0 mm RT.article The rate of cultivation has changed from 0.7 to 0.4 mm/min according to the program. The crystal and the crucible was rotated in opposite directions. The rotation frequency of the crystal 20 rpm remained constant throughout the growth process. The initial speed of the crucible was chosen equal to 5 rpm and then changed according to the program, which was implemented in microprocessor complex KM (on the basis of LIUs hardware-2) taking into account the previously calculated length of the crystal grown from different parts of the crucible. When growing from the cylindrical part of the crucible (the length of the crystal from 0 to 300 mm) Wtincreased by 0.35 rpm per inch of length, the production of the spherical part of the crucible (the length of the crystal from 300 to 450 mm) Wtand decreased by 0.3 rpm per inch of length of the crystal. Next on the same setup grown crystals of the same diameter and marks in accordance with the proposed method with the boundary values , with parameters outside of the suggested ranges and in accordance with the prototype. In all described cases, provided the condition Wkr>Wtduring the whole process of cultivation. Other process conditions were identical with the above.

Measurement of No was carried out in the Central region, three from the results of changes), as well as data on the length of the dislocation part of the crystal shown in the table. In addition, the crystal grown in accordance with the mode table 2, was carried out a more detailed study No (every 3 cm). The results of the measurement of No by the length of the crystal, as well as program changes Wtwhen pulling such a crystal from the melt located in different parts of the crucible shown in the drawing.

As can be seen from the table, and drawing, crystals grown in accordance with the proposed method (modes 1 to 3), characterized by high uniformity of distribution of oxygen along the length (No6,0%). The cylindrical part of all of the crystals has a good shape, the length of the dislocation is in the range of 420 to 450 mm In the case above upper bounds (4) and below the lower border (mode 5) of the proposed range, the degree of heterogeneity of the distribution of oxygen increases significantly, and is within (or 8.2 to 9.6)% Crystal grown in accordance with the prototype (mode 6), had a low homogeneity volume of distribution No (10,3%). In addition, due to the high Wkringots grown in modes 4 and 6, had a curved shape.

Thus, unlike the prototype, the proposed method on the crystal. This allows to significantly increase the output suitable for growing single crystals with normalized for a given level of oxygen, which is used in the manufacture of integrated circuits with a high level of integration.

1 is a Method of growing silicon single crystals by pulling on a rotating seed crystal from the melt in the crucible, the surface of which is successively from cylindrical and spherical parts, including changing the frequency of rotation of the crucible and the maintenance of a constant rotation frequency of the crystal, characterized in that the rotational speed of the crucible for growing a crystal of the cylindrical part of the crucible to increase by 0.2 to 0.5 rpm, the production of the spherical part of the crucible is reduced by 0.15 to 0.45 rpm per inch of length of the crystal.

 

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FIELD: Czochralski method for crystal growth from melt, in particular crystals of heat-resistant multicomponent compounds.

SUBSTANCE: single crystal lithium aluminate LiAlO2 is obtained by using Czochralski method in inductive heating equipment. Crystal growth process includes batch melting containing lithium aluminate in iridium crucible followed by single crystal drawing from melt onto oriented seed crystal in inert gas atmosphere. Beforehand prepared batch-cake obtained by compounding of aluminum oxide and lithium carbonate, wherein lithium carbonate excess is 2-4 % in respect to stoichiometric ratio, is used as raw batch. Mixture is heat treated in two steps: at temperature 700oC in the first step and at 1050oC in the second one with holding for 3 h in each step. To prevent losses of volatile batch components crystallization is carried out under excess (not less than 0.3 atm) pressure of inert gas, and at the beginning of growth process broader surface square is screened, seed crystal is grown up to diameter equal to 0.8 of crucible one, then crystal is drawn up to desired length while finished diameter is decreased up to 0.5-0.6 of crucible one. As a result reusable crystal part has form of truncated cone. Single crystal lithium aluminate produced according to present invention is useful in disc production served as substrate in epitaxial film growth, in particular gallium nitride (GaN) films.

EFFECT: coarse-grained crystals of high quality.

1 ex, 1 tbl, 1 dwg

FIELD: crystal growth.

SUBSTANCE: method comprises crystal growing in two stages: growing alloyed crystals used for making blanks of seeds made of a disk of a given diameter and approximately 5-6-mm thick and subsequent growing of nominally pure crystals.

EFFECT: enhanced quality of crystals.

3 dwg

FIELD: crystal growth.

SUBSTANCE: method comprises crystal growing in two stages: growing alloyed crystals used for making blanks of seeds made of a disk of a given diameter and approximately 5-6-mm thick and subsequent growing of nominally pure crystals.

EFFECT: enhanced quality of crystals.

3 dwg

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