CS203425B1 - Method of preparing monocrystalline epitax layer - Google Patents

Description

The present invention relates to a process for the preparation of a single crystalline epitaxial layer by a liquid-temperature-epitaxial-temperature-planar-saturation-saturation method.

Monocrystalline layers of semiconducting or magnetic substances are presently prepared in several ways, which can be separated according to the state of the substance from which the crystal grows. One of the main methods of crystallization is growth from the gas phase. The monocrystalline layers are obtained from the gas phase almost exclusively by so-called steam epitaxy.

Much of the crystallization methods for the preparation of the layers are based on growth from the liquid phase, namely the solution in the melt, or high temperature solution. These are liquid epitaxy methods, which include apparatus flipping, in which the solution is saturated in one position from a source of semiconductive material and by flipping it into the working position the substrate is flooded with this solution. During cooling, a layer crystallizes on the substrate. The growth is interrupted by flipping back so that the remaining melt is poured away from the growth region.

Other methods include submerging the substrate in a horizontal or vertical position. The substrate plate mounted on the holder is immersed in a saturated high temperature flow, where the crystalline layer grows as it cools.

Finally, there are shear wiping methods, cassette or spool. A massive graphite block with holes containing the solution in the melt is moved on the base plate with the embedded substrate. By sliding this block, the solution is brought into contact with the substrate. After the growth is complete, the block is displaced again, wiping the remaining solution from the substrate.

The moving solvent method used for the preparation of small volume crystals is also related to these methods. This method utilizes a temperature gradient that causes a thin zone of solution spread across an area between two crystals, both seed and saturation. The layer grows at the cooler interphase interface and dissolves on the other, thereby causing said zone movement from the seed to the substrate.

In flipping and dipping methods, a large volume of solution is necessary, which entails greater problems _; with control of its' homogeneity. Moreover, these methods are not isothermal, so that the grown layer exhibits a concentration gradient. The slide or cassette method may be isothermal, but as a result of the gradual depletion of the solution, a concentration gradient also occurs. Method,. which utilizes gas phase feed in a cassette configuration, needs a relatively bulky and complex apparatus, reducing the potential for industrial use. Moving solvent method! It is intended for the cultivation of volumetric single crystals, albeit limited in size. As the molten zone progresses along the temperature gradient, the temperature changes continuously and thus a concentration gradient is formed in the grown crystal.

According to the invention, these processes are overcome by a process for the preparation of a single crystalline epitaxial layer of a semiconducting material consisting of a compound of the type A ⁿⁱ B ^v , A ^u B ^V1 , A ^u B ^iv C2 ^v , A'B ⁿⁱ C2 ^VI , A ¹ ^ ¹ ^ ¹ ,

And ¹ is copper, silver,.

And ⁿ is zinc, cadmium, mercury,

A ¹¹¹ is aluminum, gallium, indium,

^White is aluminum, gallium, indium :,

B ^lv is silicon, germanium, tin,

B ^v is phosphorus, arsenic, antimony,

B ^V1 is sulfur, selenium, tellurium,

C ^v is nitrogen, phosphorus, arsenic, antimony,

^VI · C is sulfur, selenium, tellurium, and wherein the subscript denotes the number of atoms in the molecule or a solid solution containing these compounds or a compound of the formula R _{3 x} _ R _{x y} My Fe5_ Oi2 _y (I) wherein

R and R ‘are lanthenlds and yttrium,

Me is aluminum or gallium, x is 0 to 3, y is 0 to 5.

It consists in that the semiconductor or compound of formula (I) sheet is coated with a layer of solvent based on molten salts, metals and their oxides and is subjected to dissolution at a temperature lower than the melting or decomposition point of the substance until saturation, then approached and coupled via a saturated solvent to a substrate plate, the temperature of which is 1 to 45 K lower than the plate temperature after saturation. ^:

The proposed process carries the advantages of the latter method, but in contrast to it, it has a substantial advantage, namely isothermal throughout the growth. This property results from the fact that the proposed method is used for a thin layer (up to 10 μπι]. Movement of the zone over such a short distance in the direction of the temperature gradient means practically negligible temperature change and hence minimum concentration gradient in the thickness of the grown layer.

Holders with independent internal heating make it easy to reach the working temperature and set the temperature gradient, starting from zero to zero. Due to the variability of the holders in terms of their relative position, the whole process can be divided into two stages, first saturating the solution in contact with the source and then bringing the solution into contact with the substrate so that the actual growth occurs. The suction hole solution allows the use of virtually any plate shape, the size of which is limited by the bottom pitch of the suction holes and, on the other hand, the size of the working space. Growing in a narrow gap between the plates does not contaminate with unwanted impurities from the walls of the work area. Diffusion of impurities from the holders across the source plate or substrate need not be considered due to the slowness of the diffusion processes in the solid.

The method according to the invention is described in more detail below with reference to the accompanying drawing, in which a cross-section of both brackets and other examples is shown. Example 1

The experiment was carried out with the homoepitaxial growth of GaAs from solution in the Ga melt. The ground and polished plates of GaAs orientation (110) were split by splitting into squares of approximately 7X7 mm ² . These square plates were degreased with chloroform and then etched in H 2 SO 4: H 2 O 2: H 2 O at a ratio of 3: 1: 1 for 5 minutes. Two plates were used for the next procedure, one source and the other substrate. After rinsing with deionized water and drying, the source plate 2 was gripped by an auxiliary suction cup and placed on the suction holes 3 of the bottom holder with the upper holder 1 removed. 120 mg of highly pure Ga was placed on this plate with the same formulation. This was followed by the creation of a vacuum for: suction of the plate. A substrate plate was placed on the openings of the upper removed holder 1 and the holder was inserted into the working space so as not to touch the gallium yet. The entire apparatus was then purged several times with hydrogen. Filling the apparatus with a hydrogen atmosphere at a positive pressure of approximately 5 bar. 10 ³ Pa finished preparation. This was followed by the connection of the internal ¹ heating of the 4 holders via a thermocouple-controlled controller 5 to the power supply and heating to the set temperature. On the basis of the phase diagram of the Ga-As system, a crystallization temperature such as 720 ° C was selected. Thermal. gradient between source and substrate was. maintained at 15 ^b C / mm. At working temperature, molten gallium from the GaAs source plate was saturated. Vibration can be applied to accelerate crystallization and increase solution homogeneity. After 5 to 15 minutes, the two plate holders were brought closer to each other at a distance of 0.3 mm, so that the substrate was wetted with the GaAs solution in the Ga melt. Growth was then continued for two hours. At the end of the growth, the holders moved apart and cooled at a rate of 0.4 ° C / s up to 150 ° C. At this temperature, the heater was turned off and the hydrogen supply was stopped at 100 ° C. Residual solvent was etched from the plates in HCl. Only a layer of GaAs remained on the substrate.

Example 1 a d 2

Epitaxial growth was also applied to prepare a single crystal layer of a solid solution of Alo, 35Gao, 65As with heteroepitaxis on GaAs substrates. Saturation plates of the same composition as the solid solution, i.e., Alo, 35Gao, 65As, were made of polycrystalline material prepared separately. Both pad and saturation plates were treated in the same manner as in Example 1; They were also placed in the apparatus in the same way as Ga. The next procedure was quite similar to the one shown in the example

1. The crystallization temperature ranged from 650 to 710 ° C and was always constant for each experiment. Growth was carried out for 2 to 4 hours. After his completion, the procedure was again identical to Example 1.

Example 1 a d 3

The preparation of the epitaxial layer of semiconductive compound CdTe on a support of the same composition, ie CdTe, was carried out in the same manner as in the previous examples. This was the case of homoepitaxis. Cd was used as solvent. The crystallization temperature ranged from 700 to 800 ° C and was always constant for each experiment. Growth was 2 hours. Again, the procedure was exactly the same as the previous examples. Example 4

The preparation of the ternary semiconductive compound CdSnP2 in the form of a single crystalline epitaxial layer was carried out by heteroepitaxy on monocrystalline InP substrates. Saturation plates from polycrystalline CdSnPž were prepared separately. Further treatment of the pads and saturation plates was similar to Example 1. The etchants used: HNO 3: HCl 1: 1 and HF: HNO 3: CH 3 COOH 3: 5: 3. The crystallization temperature ranged from 400 to 550 ° C and was always constant for each experiment. Growth was 2 hours. The procedure was again identical to the previous examples.

Example 5

The preparation of the ternary semiconductive compound Cd1mTe1 in the form of a single crystal epitaxial layer was carried out by heteroepitaxy on the substrates of single crystal CdTe. Saturation plates from polycrystalline CdImTe4 were prepared separately. The treatment of the pads and saturation plates was similar to Example 1. The etching agent used: HF: HNO 3: CH 3 COOH in a ratio of 3: 5: 4. 74% of InzTe3 and 26% of CdTe were used as solvents in the crystallization. The crystallization temperature was 750 ° C. Growth was 1.5 hours. The next procedure was identical to the previous examples.

Example 6

Preparation of monocrystalline epitaxial gadolinitogallate garnet: Gd3Ga50i2 by homoepitaxis on a support of the same composition. Grinded and polished plates of orientation (111 in 7X7 mm ² dimensions were etched and HNOs for 3 minutes. After rinsing and drying, the source plate was placed in the apparatus together with a solid solvent (120 mg), which was prepared separately. composed of 92.5% PbO and 7.5% B2O3, the substrate plate was inserted in the same manner as in Example 1. The procedure is similar to Example 1, except that the apparatus was filled with argon atmosphere and temperature. the gradient between the source and the substrate was 20 ° C / mm, the crystallization temperature was constant at 1050 ° C, growth was 3 hours, the procedure was identical to the previous examples, and the solvent was removed by boiling in H3PO4 with H2SO4 .

Example 7

Preparation of single crystal epitaxial yttrium-ferric garnet: Y3Fe30i2 by heteroepitaxy on a gadolinium-gallium garnet support Gd3GasOi2 orientation (111) with dimensions 7X7 mm ² . The entire procedure is identical to that described in Example 6. The solvent (120 g) was used in the same composition as in Example 6, i.e. 92.5% PbO and 7.5% B2O3. Isothermal growth was carried out for 3.5 hours at 1000 ° C. The procedure was the same as in Example 6.

Claims (1)

A method of preparing monocrystalline epitaxial layer of semiconductor material, comprising certain compounds of type A ^AI B ^V A ^II B ^{VI, n} B ^{'in the} C2, ^{C2 in} A'B \ and ⁿ B2 ⁱⁿ 4 ^l wherein A ¹ is copper, silver, A ¹¹ is zinc, cadmium, mercury, A ¹¹¹ is aluminum, gallium, indium, Biu. is aluminum, gallium, indium, B ^lv is silicon, germanium, tin, B ^v is phosphorus, arsenic, antimony, _B vi is sulfur, selenium, tellurium, C ^v is nitrogen, phosphorus, arsenic, antimony, _c vi is sulfur, selenium, tellurium and wherein the subscripts denote the number of atoms in the molecule or solid solution based on these compounds, or a compound of formula ^1, R _{3 x} R 1 _x Fe ₅ -yMe _y O 12, (I) OF THE INVENTION. where R and R ‘Are lanthenides and ytrlum, Me is aluminum or gallium, x is 0 to 3, y is 0 to 5, characterized in that the semiconductor pad of the general formula (1j) is coated with a solvent layer based on molten salts, metals and their oxides and at a temperature lower than melting or decomposing the substance, dissolve until saturation, then approach and combine, through a saturated, solvent, with a substrate plate whose temperature is 1 to 45 K lower than the plate temperature after saturation.