On the second modification of a test method the monocrystal a is grown up directly from a gas phase on a core in the tiny quartz reactor and further measure its specific resistance.
One of manifestations of three-dimensional violations in a crystal lattice are microdefects and pretsipitata (a phase in which impurity atoms are allocated, in case of excess of level of solubility in substance at given temperatures.
At the beginning of process of growth of a monocrystal the part of an inoculating monocrystal melts for elimination of sites in it with the increased density of mechanical tension and defects. Then there is a gradual pulling of a monocrystal from fusion.
As optimum conditions of process of restoration consider temperature of 1100 — 1150 °C, the molar relation of H2: SiHCl3 in 5 — 15, density of giving of THS of 0,004 mol / (h · see. At a of cores is lower than the optimum THS degree in tetrachloride of silicon raises and the silicon exit decreases. The increase in temperature leads to essential increase of energy consumption. At the optimum molar relation of H2: SiHCl3 = 5 — 15 cores have dense fine-crystalline structure and rather equal surface. Outside these relations the rough surface is formed, the structure of cores becomes coarse-crystalline with inclusions of a gas time which at the subsequent melting of polysilicon in the course of cultivation of crystals lead to a swirling and spraying of fusion.
For receiving monocrystals -or r-type with the demanded specific resistance carry out the corresponding alloying of initial polycrystalline silicon or fusion. Enter the corresponding elements into polysilicon (, In, As, Sb, etc.) or their alloys with silicon that increases accuracy.
The considered process of sedimentation polycrystalline a is used also for receiving on its basis of pipes on carbon mandrels. Owing to high purity and durability these pipes are applied instead of quartz high-temperature processes (over 1200 °C) in furnaces in technology of semiconductor and microelectronic devices. Silicon are not subject to a prosazhivaniye or other deformation within several years of operation, despite continuous cycling between 900 and 1250 °C whereas quartz pipes have limited service life at the same processes.
Both types of defects are formed at the expense of the mechanical tension existing in a crystal and are caused by a gradient of temperature or big concentration of impurity atoms. Regional dislocations in the crystals used for production of IS, as a rule, are absent.
At a temperature above 300 °C of THS in products of reactions almost completely is absent. For increase of an exit of THS temperature of process is reduced that leads to considerable delay of a of reaction (. For increase in speed of reaction ( catalysts (copper, iron, aluminum, etc.). So, the, at introduction to initial silicon to 5% of copper the maintenance of THS in mix of products of reaction at a temperature of 265 °C reaches 95%.
on a surface of the warmed silicon cores — the bases with a diameter of 4 — 8 mm (sometimes to 30 mm) received by method a from a pedestal. In some technologies instead of cylindrical cores are used lamellar (thickness of 1 — 5 mm and 30 — 100 mm wide) with a bigger area of sedimentation. As material for cultivation of cores high-quality polycrystalline silicon serves. The surface of cores – bases is subjected to cleaning, etching in mix of acids (for example, HF+ + HNO, an otmyvka and drying. Great demands for purity are made of cores – bases for receiving polycrystalline silicon: they have to have a specific on donors> 700 Ohms · cm and on pine forest> 5000 Ohms · see.
Technically and in comparison with considered also the method of receiving polycrystalline silicon by decomposition of SiH4 silane of high purity is economically competitive. which process of receiving is as follows.
On electric measurements of test samples the residual maintenance of donors has to provide the specific resistance of silicon of n-type not less than 5000 Ohms · to cm, and on acceptors at r-type crystals — not less than 8000 Ohms · see.
Defect according to Frenkel represents vacancy and interstitial atom. Concentration of these defects is calculated also on a formula, but with great value of energy of formation of interstitial atom of W = 4,5. Vacancy and interstitial atoms move in a lattice at the expense of thermal energy.