JPH07187882A - Method for growing crystal of compound semiconductor and its production - Google Patents

Abstract

PURPOSE:To provide a method for growing a crystal capable of freely changing compsn. ratios according to precipitation and growth of the crystal at the time of growing the crystal of a compd. semiconductor from a liquid phase and capable of maintaining the specified compsn. ratios of crystals even in the case of growing of such mixed crystals which have elements of large coeffts. of segregation and its apparatus. CONSTITUTION:One or more elements X to be subjected to compsn. ratio control among the plural semiconductor elements are melted in respectively discrete or common auxiliary vessel 2 in the method for growing the crystal of the compd. semiconductor from a raw material liquid consisting of plural semiconductor elements and its apparatus. These elements to be subjected to the compsn. ratio control are then supplied from the auxiliary vessel 2 to a main vessel 1 through an element permeable sluice plate 4 capable of controlling the permeation rate of the elements to form the raw material liquid a, by which the compsn. ratios of the crystal A to be grown from this raw material liquid are arbitrarily controlled.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for growing a crystal of a compound semiconductor from a liquid phase and an apparatus therefor, and more particularly to a crystal growth method and an apparatus therefor capable of arbitrarily controlling the composition ratio of precipitated crystals. Is.

[0002]

2. Description of the Related Art As a method for growing a solid phase crystal from a liquid phase of a semiconductor raw material, a liquid phase epitaxial method, a pulling method and the like are known. As the liquid phase epitaxial method, a molten low melting point metal is used as a solvent, and a semiconductor raw material for the purpose of crystal growth is dissolved therein, and then the solution is cooled,
A crystal growth method (gradual cooling method) in which the semiconductor crystals are deposited as a thin film on the substrate, a temperature difference is provided in the raw material melt, the raw material material is melted on the high temperature side, and brought into contact with the substrate on the low temperature side (temperature difference). Law) etc. The pulling method is a method in which a semiconductor raw material is melted, a seed crystal is brought into contact with a melt, and then the seed crystal is gradually pulled up to grow a crystal after the seed crystal to obtain a bulk crystal.

[0003]

In the method of growing a solid-phase compound semiconductor crystal from a liquid phase as described above,
It is desired to freely change the composition ratio of the crystal in the direction in which the crystal grows, that is, as the thickness of the crystal increases to impart various characteristics. On the other hand, when an element having a large segregation coefficient is present in a mixed crystal composed of three or more elements, the difference in the amount of precipitation of each element causes
There is a problem that the composition ratio varies in the crystal growth direction, and a good thick film crystal cannot be obtained. The segregation coefficient is a ratio (ratio between a composition in a liquid phase and a composition in a solid phase) in which a raw material element in a solution / melt is incorporated into a crystal.
When the segregation coefficient of a certain element X is larger than that of another element, the element X precipitates better in the crystal than other elements, and the proportion of the element X in the solid phase is larger than that in the liquid phase. Will be bigger. Therefore, the amount of the element X remaining in the liquid phase is drastically reduced as compared with the amounts of the other elements, and as a result, the composition of the element X in the solid phase is also reduced as the crystal growth progresses. Will be done. Therefore, when growing a mixed crystal of three or more elements having an element with a large segregation coefficient from the liquid phase, it is desired to keep the composition ratio of the crystal constant.

In response to the above demand, the object of the present invention is to allow the composition ratio of the compound semiconductor to be continuously and freely changed as the crystal precipitates and grows when the crystal of the compound semiconductor is grown from the liquid phase. A crystal growth method and an apparatus therefor are provided. Further, this makes it possible to always maintain a constant composition ratio even when growing a mixed crystal containing an element having a large segregation coefficient.

[0005]

Means for Solving the Problems In the present tank in which raw material liquids are mixed and crystal growth is performed, the present inventors have melted only the elements whose composition ratio is controlled in another melting tank. Then
By changing the composition ratio of the element in the main tank to an arbitrary value by feeding and diffusing the element into the main tank in an arbitrary amount,
Further, the present invention has been completed by making it possible to keep the composition ratio constant against unintended changes. That is, the crystal growth method of the present invention is a method for growing a crystal of a compound semiconductor from a raw material liquid composed of a plurality of semiconductor elements, and one or more elements to be controlled in composition ratio among the plurality of semiconductor elements. Are melted in separate or common sub-vessels, and the element whose composition ratio is to be controlled is passed through an element-permeable sill plate (hereinafter, referred to as “shar plate”) capable of controlling the passage amount of the element. The composition of the present invention is characterized in that the composition ratio of the crystals grown from the raw material liquid is arbitrarily controlled by supplying the raw material liquid from the tank to the main tank. Further, when the element targeted for the composition ratio control has a larger segregation coefficient than other elements, the crystal growth method of the present invention controls the composition ratio of the growing crystal to be always constant. It is profitable. However, the method for growing a compound semiconductor crystal is
A liquid phase epitaxial method may be used, or a pulling method may be used.

Further, an apparatus for carrying out the crystal growth method according to the present invention (hereinafter referred to as "crystal growth apparatus") is
It has one or more sub-tanks and one main tank, and the sub-tanks and the main tank are communicated with each other through a plate that can control the passage amount of the elements in the sub-tank, and the sub-tank has a composition ratio control. The target element is melted or melted, and the element in the sub tank is supplied to the main tank through a divider plate in a desired amount to form a raw material liquid, and the composition ratio is arbitrarily adjusted from the raw material liquid in the main tank. It is possible to grow a controlled compound semiconductor crystal. In the present specification, “melting an element” includes “melting an element as a solute in a solvent which is heated and melted” and “melting an element”.

The crystal growth method of the present invention will be specifically described below with reference to the drawings showing the apparatus. FIG. 1 is a diagram schematically showing an example of carrying out the crystal growth method of the present invention.
As shown in the same figure, the crystal growth method of the present invention uses a crystal A of a compound semiconductor from a raw material liquid a in which plural semiconductor elements are melted.
In the method of growing a plurality of semiconductor elements, for example, if the plurality of semiconductor elements are ternary elements of X, Y, and Z, the element X to be controlled in composition ratio, that is, in order to control the composition ratio, The element X for which the supply amount to the main tank is controlled is melted in the sub tank 2, the remaining elements Y and Z are melted in the main tank 1, and the element X
Are supplied from the sub tank 2 to the main tank 1 through the dividing plate 4 having the permeation holes 3 capable of controlling the passage amount of the element X and diffuse-mixed to form the raw material liquid a. The composition ratio of the crystal A grown from the raw material liquid a is controlled to an arbitrary value by freely controlling. However, this figure is an example of the case where the mechanism relating to the precipitation of the crystal is the liquid phase epitaxial method utilizing the temperature difference method, and the crystal A is precipitated and grown on the substrate 5.

As the compound semiconductor composed of a binary element, a group III-V (B, Al, Ga, In, etc.) / Group V (N, P, As, Sb, etc.) combination is used.
Group compounds, Group II (Zn, Cd, Hg, etc.) and Group VI (S,
II, VI group compounds and the like by a combination of Se, Te and the like). For crystal growth of these compound semiconductors, the present invention contributes to suppressing deviation of the crystal composition ratio from the stoichiometric composition ratio. For example, GaAs
In addition to causing various lattice defects due to deviation of the composition ratio, etc., there is a problem that AlSb, GaSb, etc. become high-concentration P type, and InAs becomes N type. It becomes one of the means.

Compounds of Group III-V are representatively exemplified as the compound semiconductor of the above-mentioned compound semiconductor of ternary or more. For example, A, B, C are group III elements,
If D, E, and F are group V elements and x and y are the existence probabilities of each element (0 ≦ x ≦ 1, 0 ≦ y ≦ 1), a ternary mixed crystal is obtained: A _x B _1-x D, AD _y E _1-y , as a quaternary mixed crystal, (A _x B _1-x ) _y C _1-y D, A
(D _x E _1-x ) _y F _1-y , A _x B _1-x D _y E _1-y .
There are multiple elements such as hexagonal mixed crystals. As a combination of the elements of the ternary mixed crystal, AlGaAs, AlGa
Sb, GaInP, GaInAs, GaPAs, etc. are exemplified, and as the quaternary mixed crystal, (AlGa) AsSb, (A
lGa) InP, (AlGaIn) As, (GaIn)
PAs, (GaIn) AsSb, In (PAsSb) A
Examples are s and the like. The composition ratio of such a multi-element mixed crystal can be freely changed, and thus the crystal growth method of the present invention is effectively applied. That is, by the crystal growth method of the present invention, the composition ratio of these compound semiconductors changes continuously with respect to the crystal growth direction, and the rate of change of the composition ratio can be manipulated arbitrarily. Becomes For example, from AlGaAS to AlA
It is also possible to form a material whose composition ratio changes to S continuously.

When the compound semiconductor is a ternary or more mixed crystal, and an element having a large segregation coefficient is present in the mixed crystal, the fluctuation of the composition ratio poses a problem as described above. AlGa
Typical examples are Al in As and P in InGaAsP. When such a compound semiconductor crystal is deposited and grown from a liquid phase to a solid phase, Al and P in the growth layer are formed.
The composition ratio is gradually reduced in the thickness direction, and it becomes difficult to maintain a uniform composition ratio when growing a thick film. For the crystal growth of such compound semiconductor, the crystal growth method of the present invention is a useful means for stabilizing the composition ratio. That is, since the crystal growth method of the present invention can continuously change the composition ratio of the multi-element mixed crystal in the crystal growth direction as described above, as a special case of composition ratio control, the segregation coefficient is Even if the composition ratio in the thickness direction fluctuates, which is a cause, this can be controlled to be constant.

Of the multi-element elements, the number of elements whose supply amount is controlled to control the composition ratio is 1 or more, and all the components of the multi-element mixed crystal are the object of composition ratio control. It may be. The element whose supply amount is to be controlled is melted in the sub tank and only the amount necessary for control is supplied to the main tank. When there are a plurality of elements for which the supply amount is controlled, melting of each element is performed in a separate sub tank, or
It may be selected depending on the purpose whether all the elements are melted in one sublayer, or only some of the elements are melted in a common subtank and the rest are melted in individual subtanks.

The partition plate is for passing the required controlled amount of the element whose composition ratio is to be controlled from the sub tank to the main tank. The passage amount of the element is controlled mainly by changing the hole diameter of the permeation holes, the total length of the holes, and the number of the holes provided in the partition plate, but it may be controlled by a method of opening and closing the permeation holes with a predetermined intermittent time. . Specific modes of the plate and the transmission hole will be described in detail in the description of the crystal growth apparatus described later.

The mechanism of crystal precipitation itself is based on the principles of known liquid phase epitaxial method and pulling method. Fig. 1 is an example of the case where precipitation is performed by the principle of the liquid phase epitaxial method. A low melting point metal is heated and melted in the main tank and the sub tank to form a solvent, and a predetermined source element is solute in each tank. And melt to control the composition ratio. When the crystal precipitation is based on the principle of the pulling method, the raw material elements are heated and melted in each predetermined melting tank, and the composition ratio of the raw material liquid in the main tank is controlled.

[0014]

[Function] Isolation of the element whose composition ratio is to be controlled in the sub tank,
With the configuration in which only the required control amount is sent from here to the main tank, the composition ratio of the elements in the raw material liquid in the main tank can be freely controlled. Therefore, as the precipitation of crystals progresses from the liquid phase to the solid phase, the growing crystal can be controlled by controlling the composition ratio of the elements in the raw material liquid at an arbitrary rate of change (including the case of keeping it constant). The composition ratio of can be similarly controlled.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An apparatus for carrying out the crystal growth method of the present invention (hereinafter referred to as "crystal growth apparatus") will be described below with reference to the drawings. [Embodiment 1] This embodiment shows a basic configuration example of a crystal growth apparatus in the case of controlling the supply amount of one element X among the elements forming the compound semiconductor XYZ for controlling the composition ratio. FIG. 1 is a diagram schematically showing an example of the configuration of the crystal growth apparatus. As shown in the figure, the crystal growth apparatus of the present invention has a sub-tank 2 and a main tank 1, and the sub-tank 2 and the main tank 1 each have a permeation hole 3 capable of controlling the passage amount of an element. The element X, which is communicated through the divider plate 4, is heated and melted in the sub tank to be supplied for controlling the composition ratio, and the element X is supplied in the main tank.
The remaining elements Y and Z other than the above are melted by heating, and the element X in the sub tank is diffused and mixed into the main tank through a plate in a desired amount to form a raw material liquid a. It is an apparatus capable of growing a crystal A of a compound semiconductor whose composition ratio is arbitrarily controlled. The above crystal growth apparatus is an example corresponding to crystal precipitation by the liquid phase epitaxial method, and the crystal A is deposited and grown on the substrate 5.

The main tank 1, the sub tank 2, and the substrate 5 may have an integral structure or a separable structure. A slide boat 7 having a main tank 1 and a sub tank 2 as shown in FIG.
However, the structure may be such that it slides with respect to the substrate holder 8 having the substrate 5. Examples of materials for the main tank 1, the sub tank 2, and the substrate holder include graphite, glassy carbon, p-BN, and SiO ₂ .

In addition to heating means (not shown) such as a heater for melting the raw material, the main tank 1 and the sub tank 2 are provided with heating means 6 for locally controlling the temperature of the raw material liquid. It is preferable. By using the heating means to change the temperature between the upper and lower sides of the raw material liquid, the growth raw material can be transferred from the high temperature side to the low temperature side, and the crystal can be grown on the substrate. An electric heater is generally used as the heating means. As a mode of the heating means, as shown in FIG. 1, a configuration in which the heating means 6 is provided from the upper part of the main tank to the divider plate, and as shown in FIG. 2, in addition to the heating means 6 of FIG. Examples thereof include a configuration in which the heating means 6b is provided, and a configuration in which multiple stages of heating / cooling means are provided on the wall surface of the melting tank to finely control the temperature change of the raw material liquid. This makes it possible to control the speed at which the elements in the sub tank diffuse into the main tank,
The composition of the growth film can be changed.

The partition plate 4 is provided with a permeation hole 3 which connects the sub tank and the main tank, and is used to supply a desired amount of the element whose composition ratio is to be controlled from the sub tank to the main tank. . The material for the plate is graphite, glassy carbon, p-BN, S, as in the above substrate holder.
iO ₂ or the like can be used. The mode of the permeation holes for the plate is not limited to linear through holes, sponge-like irregular porosity, etc., but linear through holes are more practical and preferable. The pore diameter of the permeation hole 3, the number of pores, and the total length of the pores are important factors for determining the amount of passage of the element, and the optimum values can be freely selected theoretically or experimentally along with the temperature control of the liquid. do it. Further, as shown in FIG. 3, a shutter may be provided in the transmission hole and the passage amount of the element may be controlled by the opening time of the transmission hole. FIG. 3 (a) is an example in which all the transmission holes are opened and closed by one plate 4b, and FIG. 3 (b) is
This is an example of opening and closing by changing the hole diameter depending on the positional relationship between the transmission hole 3b provided in the plate 4b and the transmission hole 3 provided in the cut-off plate 4.

[Experimental Example] Using the above crystal growth apparatus, AlGa having a large segregation coefficient was difficult to achieve in the past.
An experiment of liquid phase epitaxial growth of As was performed. Ga as a solvent was melted at 850 ° C., Al was dissolved in the sub tank, Ga and As were melted in the main tank, and the furnace temperature was set to 8
Keep the temperature at 50 ℃, and about 5 ℃ between the top and bottom of the solution by the local heater.
The crystal growth was carried out with a temperature difference of. The obtained Al _0.6
When the composition ratio of Ga _0.4 As was examined in the thickness direction, it was found to be constant, and the crystal growth method and the apparatus thereof of the present invention can control the composition ratio of crystals, and especially for those containing an element with a large segregation coefficient. It was confirmed that the fluctuation of the composition ratio can be effectively suppressed.

[Embodiment 2] In this embodiment, as one of the variations of the apparatus shown in Embodiment 1, a crystal growth apparatus in the case where a plurality of elements whose supply amount is controlled for controlling the composition ratio are plural. Shows the configuration of. FIG. 4 is a diagram schematically showing the structure of the crystal growth apparatus in the case where the supply amount control target is two elements. As shown in the figure, the crystal growth apparatus is the same as the apparatus of Example 1 except that two sub-tanks 2a and 2b are provided in parallel and the elements whose composition ratio is to be controlled are melted in each. Is.

With the above-described crystal growth apparatus, the composition ratio of a plurality of elements can be controlled when liquid phase epitaxial growth of a multi-element mixed crystal such as InGaAsP is performed as in the first embodiment. As for the number of sub-vessels, all the elements whose supply amount is to be controlled may be provided individually, or in parallel as many as necessary for melting some elements in a common vessel.

[Embodiment 3] This embodiment shows the structure of a crystal growth apparatus in the case where the principle of crystal precipitation of a compound semiconductor is based on the pulling method. FIG. 5 is a diagram schematically showing an example of the structure of the crystal growth apparatus. The crystal growth apparatus is provided with a plurality of sub-tanks (not shown in the figure, except for 2a and 2b) around the main tank 1, and the sub-tanks and the main tank control the passage amount of elements. Function of each part, except that the bulk crystal B of the mixed crystal is pulled up from the upper liquid surface of the main tank by a well-known pulling method. Is the same as the device of the first and second embodiments.

With the crystal growth apparatus as described above, the component ratio can be freely controlled even when pulling a bulk crystal of multiple components. In particular, it has become possible to obtain a bulk crystal in which fluctuations in the composition ratio are suppressed for those containing an element with a large segregation coefficient.

In addition to the example of controlling the composition ratio of the compound semiconductor as detailed above, the method and apparatus of the present invention are also useful for controlling the concentration of impurities (dopants) added to the compound semiconductor for crystal growth. is there. For example, when the carrier concentration is constant in the thickness direction of the crystal,
Alternatively, when changing continuously in the thickness direction, an impurity element (Zn, Te, Si in the case of a III-V group semiconductor is used).
Etc.) as a material to be supplied from the sub tank to the main tank, and the impurity concentration can be freely controlled by controlling the addition amount in the same manner as described above.

[0025]

As described in detail above, when the crystal growth method and the apparatus thereof according to the present invention are used to grow a compound semiconductor crystal from a liquid phase such as a liquid phase epitaxial method or a pulling method, the crystal is precipitated and grown. As such, the composition ratio and / or the amount of impurities added can be continuously and freely changed. Further, conventionally, it has been difficult to form a mixed crystal containing an element having a large segregation coefficient into a thick film with a constant composition ratio by crystal growth by the liquid phase epitaxial method. Even with the crystal growth method, the composition ratio can be constantly maintained in the thickness direction of the crystal.

[Brief description of drawings]

FIG. 1 is a schematic view showing an example of the configuration of a crystal growth apparatus for specifically carrying out the crystal growth method of the present invention.

FIG. 2 is a schematic diagram showing an example of a mode of heating means.

FIG. 3 is a schematic view showing an example of a mode of a shutter provided in a transmission hole of a divider plate.

FIG. 4 is a schematic diagram showing a structure of a crystal growth apparatus in the case where two elements whose supply amounts are controlled are two.

FIG. 5 is a schematic diagram showing an example of a configuration of a crystal growth apparatus in the case where a method for growing a crystal of a compound semiconductor is a pulling method.

[Explanation of symbols]

 A crystal of compound semiconductor a raw material liquid X to Z elements constituting compound semiconductor 1 main tank 2 sub tank 4 element permeable threshold plate

Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI Technical display location C30B 29/40 B 8216-4G C 8216-4G H01L 21/208 Z

Claims (5)

[Claims] 1. A method for growing a crystal of a compound semiconductor from a raw material liquid comprising a plurality of semiconductor elements, wherein one or more elements to be subject to composition ratio control are individually or individually selected from the plurality of semiconductor elements. Melting in a common sub-tank, the element to be subject to the composition ratio control, by forming a raw material liquid from the sub-tank to the main tank through an element permeable divider plate that can control the passage amount of the element, A crystal growth method, wherein the composition ratio of crystals grown from the raw material liquid is arbitrarily controlled. 2. The element whose composition ratio is to be controlled has a larger segregation coefficient than other elements, and the composition ratio of the crystals grown from the raw material liquid is controlled to be always constant. The crystal growth method according to claim 1. 3. The raw material liquid is obtained by dissolving a plurality of semiconductor elements in a heated and melted solvent, and the method for growing a crystal of a compound semiconductor is a liquid phase epitaxial method. Crystal growth method. 4. The crystal growth method according to claim 1, wherein the raw material liquid is formed by melting a plurality of semiconductor elements, and the method for growing the crystal of the compound semiconductor is a pulling method. 5. It has one or more sub-tanks and one main tank, and the sub-tank and the main tank are communicated with each other through an element-permeable dividing plate capable of controlling the amount of passage of elements in the sub-tank, In the sub-tank, the element whose composition ratio is to be controlled is melted or melted, and the element in the sub-tank is supplied to the main tank through the plate in a desired amount to form a raw material liquid. A crystal growth apparatus capable of growing a compound semiconductor crystal whose composition ratio is arbitrarily controlled from the raw material liquid.